From 16fa40b893054d8bd7f13625f204bf02d74a27b5 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Fri, 18 Mar 2016 15:50:24 -0700
Subject: [PATCH 01/25] (1) add a var/cache directory under spack. (2)
 downloads from URLFetchStrategy check the cache and skip the download if the
 source is available there.

---
 lib/spack/spack/__init__.py       |  2 ++
 lib/spack/spack/fetch_strategy.py | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index 0ba42bbbfcd..22436e46c43 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -46,6 +46,8 @@
 stage_path     = join_path(var_path, "stage")
 repos_path     = join_path(var_path, "repos")
 share_path     = join_path(spack_root, "share", "spack")
+cache_path     = join_path(spack_root, "var", "cache")
+mkdirp(cache_path)
 
 prefix = spack_root
 opt_path       = join_path(prefix, "opt")
diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 0d0a7db8a91..3a774a35cd9 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -156,6 +156,11 @@ def fetch(self):
         if self.archive_file:
             tty.msg("Already downloaded %s" % self.archive_file)
             return
+        cached = self.check_cache()
+        if cached:
+            tty.msg("Cached %s." % cached)
+            shutil.copy(cached, "./")
+            return
 
         tty.msg("Trying to fetch from %s" % self.url)
 
@@ -211,6 +216,9 @@ def fetch(self):
 
         if not self.archive_file:
             raise FailedDownloadError(self.url)
+        else:
+            shutil.copy(self.archive_file, spack.cache_path)
+
 
     @property
     def archive_file(self):
@@ -283,6 +291,17 @@ def check(self):
                     "%s checksum failed for %s" % (checker.hash_name, self.archive_file),
                     "Expected %s but got %s" % (self.digest, checker.sum))
 
+
+    def check_cache(self):
+        if not self.digest:
+            return
+        checker = crypto.Checker(self.digest)
+        paths = (join_path(spack.cache_path, f) for f in os.listdir(spack.cache_path))
+        for p in paths:
+            if checker.check(p):
+                return p
+
+
     @_needs_stage
     def reset(self):
         """Removes the source path if it exists, then re-expands the archive."""

From ac7323118e9c3ddfc7b27992e545e59de2f32c7f Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Fri, 18 Mar 2016 16:34:45 -0700
Subject: [PATCH 02/25] rename for clarity

---
 lib/spack/spack/fetch_strategy.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 3a774a35cd9..73083a0f5ab 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -156,7 +156,7 @@ def fetch(self):
         if self.archive_file:
             tty.msg("Already downloaded %s" % self.archive_file)
             return
-        cached = self.check_cache()
+        cached = self.search_cache()
         if cached:
             tty.msg("Cached %s." % cached)
             shutil.copy(cached, "./")
@@ -292,7 +292,7 @@ def check(self):
                     "Expected %s but got %s" % (self.digest, checker.sum))
 
 
-    def check_cache(self):
+    def search_cache(self):
         if not self.digest:
             return
         checker = crypto.Checker(self.digest)

From fd067dd8b888ac4c2cc6cacec44d2ba978b04e8a Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Fri, 18 Mar 2016 17:00:13 -0700
Subject: [PATCH 03/25] since only archives with checksums can be retrieved
 from the cache, make sure that an archive without a checksum isnt placed
 there (this wouldn't cause an error but does waste space and might be
 confusing)

---
 lib/spack/spack/fetch_strategy.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 73083a0f5ab..27fb38b7a6b 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -216,7 +216,7 @@ def fetch(self):
 
         if not self.archive_file:
             raise FailedDownloadError(self.url)
-        else:
+        elif self.digest:
             shutil.copy(self.archive_file, spack.cache_path)
 
 

From d632266a40e8d472892991144391b1862231fec0 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Fri, 18 Mar 2016 17:15:45 -0700
Subject: [PATCH 04/25] move cache to var/spack/cache

---
 lib/spack/spack/__init__.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index 22436e46c43..6fb472b15d9 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -46,7 +46,7 @@
 stage_path     = join_path(var_path, "stage")
 repos_path     = join_path(var_path, "repos")
 share_path     = join_path(spack_root, "share", "spack")
-cache_path     = join_path(spack_root, "var", "cache")
+cache_path     = join_path(var_path, "cache")
 mkdirp(cache_path)
 
 prefix = spack_root

From ee5e507ff60e56f9d83de9b7e2c19e929dcd3481 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Mon, 21 Mar 2016 20:48:12 -0700
Subject: [PATCH 05/25] pursuing a strategy using fetch.archive and treating
 var/spack/cache as a mirror. this should support both URLFetchStrategy as
 well as VCSFetchStrategy (the previous strategy supported only the former).
 this won't work until URLFetchStrategy.archive is updated

---
 lib/spack/spack/fetch_strategy.py | 17 -----------------
 lib/spack/spack/package.py        |  2 ++
 lib/spack/spack/stage.py          | 13 ++++++++++++-
 3 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 27fb38b7a6b..d1b3ce92917 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -156,11 +156,6 @@ def fetch(self):
         if self.archive_file:
             tty.msg("Already downloaded %s" % self.archive_file)
             return
-        cached = self.search_cache()
-        if cached:
-            tty.msg("Cached %s." % cached)
-            shutil.copy(cached, "./")
-            return
 
         tty.msg("Trying to fetch from %s" % self.url)
 
@@ -216,8 +211,6 @@ def fetch(self):
 
         if not self.archive_file:
             raise FailedDownloadError(self.url)
-        elif self.digest:
-            shutil.copy(self.archive_file, spack.cache_path)
 
 
     @property
@@ -292,16 +285,6 @@ def check(self):
                     "Expected %s but got %s" % (self.digest, checker.sum))
 
 
-    def search_cache(self):
-        if not self.digest:
-            return
-        checker = crypto.Checker(self.digest)
-        paths = (join_path(spack.cache_path, f) for f in os.listdir(spack.cache_path))
-        for p in paths:
-            if checker.check(p):
-                return p
-
-
     @_needs_stage
     def reset(self):
         """Removes the source path if it exists, then re-expands the archive."""
diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index b488e4c49db..d007f37aebb 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -715,6 +715,8 @@ def do_fetch(self, mirror_only=False):
         if spack.do_checksum and self.version in self.versions:
             self.stage.check()
 
+        self.stage.cache_local()
+        
 
     def do_stage(self, mirror_only=False):
         """Unpacks the fetched tarball, then changes into the expanded tarball
diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index f88f82fc2d6..8933ad6da26 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -273,6 +273,7 @@ def fetch(self, mirror_only=False):
             # the root, so we add a '/' if it is not present.
             mirror_roots = [root if root.endswith('/') else root + '/'
                             for root in mirrors.values()]
+            mirror_roots.append("file://" + os.path.abspath(spack.cache_path) + os.sep)
             urls = [urljoin(root, self.mirror_path) for root in mirror_roots]
 
             # If this archive is normally fetched from a tarball URL,
@@ -305,6 +306,7 @@ def fetch(self, mirror_only=False):
             self.fetcher = self.default_fetcher
             raise fs.FetchError(errMessage, None)
 
+
     def check(self):
         """Check the downloaded archive against a checksum digest.
            No-op if this stage checks code out of a repository."""
@@ -318,6 +320,15 @@ def check(self):
         else:
             self.fetcher.check()
 
+
+    def cache_local(self):
+        archiveDst = join_path(os.path.abspath(spack.cache_path), self.mirror_path)
+        mkdirp(os.path.dirname(archiveDst))
+        # TODO: this moves the archive for URLFetchStrategy vs. a copy - edit
+        # to do a move?
+        self.fetcher.archive(archiveDst)
+
+
     def expand_archive(self):
         """Changes to the stage directory and attempt to expand the downloaded
            archive.  Fail if the stage is not set up or if the archive is not yet
@@ -421,7 +432,7 @@ def expand_archive(self):
                 shutil.move(source_path, destination_path)
 
 
-@pattern.composite(method_list=['fetch', 'create', 'check', 'expand_archive',  'restage', 'destroy'])
+@pattern.composite(method_list=['fetch', 'create', 'check', 'expand_archive',  'restage', 'destroy', 'cache_local'])
 class StageComposite:
     """
     Composite for Stage type objects. The first item in this composite is considered to be the root package, and

From b255f02762375cee064b062837581e5466fdb908 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Mon, 21 Mar 2016 20:50:26 -0700
Subject: [PATCH 06/25] undoing whitespace-only diff

---
 lib/spack/spack/fetch_strategy.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index d1b3ce92917..0d0a7db8a91 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -212,7 +212,6 @@ def fetch(self):
         if not self.archive_file:
             raise FailedDownloadError(self.url)
 
-
     @property
     def archive_file(self):
         """Path to the source archive within this stage directory."""
@@ -284,7 +283,6 @@ def check(self):
                     "%s checksum failed for %s" % (checker.hash_name, self.archive_file),
                     "Expected %s but got %s" % (self.digest, checker.sum))
 
-
     @_needs_stage
     def reset(self):
         """Removes the source path if it exists, then re-expands the archive."""

From 41a97c8f80b8e93a7b180bd4d4a5a4286ce6f311 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Mon, 21 Mar 2016 20:55:23 -0700
Subject: [PATCH 07/25] temporarily wrap archiving with conditional to avoid
 moving (this still causes a failure on the initial download)

---
 lib/spack/spack/stage.py | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index 8933ad6da26..61faec6de94 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -323,10 +323,11 @@ def check(self):
 
     def cache_local(self):
         archiveDst = join_path(os.path.abspath(spack.cache_path), self.mirror_path)
-        mkdirp(os.path.dirname(archiveDst))
-        # TODO: this moves the archive for URLFetchStrategy vs. a copy - edit
-        # to do a move?
-        self.fetcher.archive(archiveDst)
+        if not os.path.exists(archiveDst): #tmp conditional
+            mkdirp(os.path.dirname(archiveDst))
+            # TODO: this moves the archive for URLFetchStrategy vs. a copy - 
+            # edit to do a move?
+            self.fetcher.archive(archiveDst)
 
 
     def expand_archive(self):

From 75460d8586bf62dcedaf4eb5acdb2de75f1d662a Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Tue, 22 Mar 2016 10:43:43 -0700
Subject: [PATCH 08/25] URLFetchStrategy.archive does a copy vs. a move now

---
 lib/spack/spack/fetch_strategy.py | 2 +-
 lib/spack/spack/stage.py          | 7 ++-----
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 0d0a7db8a91..fc5d7e231cf 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -268,7 +268,7 @@ def archive(self, destination):
         if not extension(destination) == extension(self.archive_file):
             raise ValueError("Cannot archive without matching extensions.")
 
-        shutil.move(self.archive_file, destination)
+        shutil.copy(self.archive_file, destination)
 
     @_needs_stage
     def check(self):
diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index 61faec6de94..54359bddce2 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -323,11 +323,8 @@ def check(self):
 
     def cache_local(self):
         archiveDst = join_path(os.path.abspath(spack.cache_path), self.mirror_path)
-        if not os.path.exists(archiveDst): #tmp conditional
-            mkdirp(os.path.dirname(archiveDst))
-            # TODO: this moves the archive for URLFetchStrategy vs. a copy - 
-            # edit to do a move?
-            self.fetcher.archive(archiveDst)
+        mkdirp(os.path.dirname(archiveDst))
+        self.fetcher.archive(archiveDst)
 
 
     def expand_archive(self):

From cb9fba98d8d0c389f3295d5d30cdb650e6ea79b7 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Tue, 22 Mar 2016 19:37:47 -0700
Subject: [PATCH 09/25] (1) relocate cache for tests (2) initial approach for
 restoring unit tests (just for git tests although the same concept applies to
 the other unit tests which are failing - namely those for svn and hg)

---
 lib/spack/spack/cmd/test.py       | 4 ++++
 lib/spack/spack/test/git_fetch.py | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/lib/spack/spack/cmd/test.py b/lib/spack/spack/cmd/test.py
index ddc6cb4fcee..9a85c7d2707 100644
--- a/lib/spack/spack/cmd/test.py
+++ b/lib/spack/spack/cmd/test.py
@@ -23,6 +23,7 @@
 # Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
 import os
+import shutil
 from pprint import pprint
 
 from llnl.util.filesystem import join_path, mkdirp
@@ -66,4 +67,7 @@ def test(parser, args):
             
             if not os.path.exists(outputDir):
                 mkdirp(outputDir)
+        spack.cache_path = join_path(spack.var_path, "test-cache")
+        mkdirp(spack.cache_path)
         spack.test.run(args.names, outputDir, args.verbose)
+        shutil.rmtree(spack.cache_path)
diff --git a/lib/spack/spack/test/git_fetch.py b/lib/spack/spack/test/git_fetch.py
index 35780441166..76814f089ad 100644
--- a/lib/spack/spack/test/git_fetch.py
+++ b/lib/spack/spack/test/git_fetch.py
@@ -30,6 +30,8 @@
 from spack.test.mock_repo import MockGitRepo
 from spack.version import ver
 
+import shutil
+import os
 
 class GitFetchTest(MockPackagesTest):
     """Tests fetching from a dummy git repository."""
@@ -49,6 +51,8 @@ def tearDown(self):
         """Destroy the stage space used by this test."""
         super(GitFetchTest, self).tearDown()
         self.repo.destroy()
+        for d in os.listdir(spack.cache_path):
+            shutil.rmtree(os.path.join(spack.cache_path, d))
 
     def assert_rev(self, rev):
         """Check that the current git revision is equal to the supplied rev."""

From ed0f6f75a7215c959431377ffe7e4faf09dc88d6 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Wed, 23 Mar 2016 19:49:28 -0700
Subject: [PATCH 10/25] clear test cache before and after each MockPackagesTest
 (I think Ive got a better way to avoid test fragility but Ill add this for
 now)

---
 lib/spack/spack/cmd/test.py                | 2 +-
 lib/spack/spack/test/git_fetch.py          | 5 -----
 lib/spack/spack/test/mock_packages_test.py | 7 +++++++
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/lib/spack/spack/cmd/test.py b/lib/spack/spack/cmd/test.py
index 9a85c7d2707..233cd186f09 100644
--- a/lib/spack/spack/cmd/test.py
+++ b/lib/spack/spack/cmd/test.py
@@ -70,4 +70,4 @@ def test(parser, args):
         spack.cache_path = join_path(spack.var_path, "test-cache")
         mkdirp(spack.cache_path)
         spack.test.run(args.names, outputDir, args.verbose)
-        shutil.rmtree(spack.cache_path)
+        shutil.rmtree(spack.cache_path, ignore_errors=True)
diff --git a/lib/spack/spack/test/git_fetch.py b/lib/spack/spack/test/git_fetch.py
index 76814f089ad..d3e1206c13b 100644
--- a/lib/spack/spack/test/git_fetch.py
+++ b/lib/spack/spack/test/git_fetch.py
@@ -30,9 +30,6 @@
 from spack.test.mock_repo import MockGitRepo
 from spack.version import ver
 
-import shutil
-import os
-
 class GitFetchTest(MockPackagesTest):
     """Tests fetching from a dummy git repository."""
 
@@ -51,8 +48,6 @@ def tearDown(self):
         """Destroy the stage space used by this test."""
         super(GitFetchTest, self).tearDown()
         self.repo.destroy()
-        for d in os.listdir(spack.cache_path):
-            shutil.rmtree(os.path.join(spack.cache_path, d))
 
     def assert_rev(self, rev):
         """Check that the current git revision is equal to the supplied rev."""
diff --git a/lib/spack/spack/test/mock_packages_test.py b/lib/spack/spack/test/mock_packages_test.py
index 6d24a84150b..85c15d4a6ad 100644
--- a/lib/spack/spack/test/mock_packages_test.py
+++ b/lib/spack/spack/test/mock_packages_test.py
@@ -125,9 +125,16 @@ def cleanmock(self):
             pkg.dependencies.update(deps)
 
 
+    def rm_cache(self):
+        shutil.rmtree(spack.cache_path, ignore_errors=True)
+
+
     def setUp(self):
+        self.rm_cache()
+        mkdirp(spack.cache_path)
         self.initmock()
 
 
     def tearDown(self):
+        self.rm_cache()
         self.cleanmock()

From dbfa6c925ec60c89004f6ccd88e985f71f650a69 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Wed, 23 Mar 2016 20:18:58 -0700
Subject: [PATCH 11/25] replace references to cache directory with references
 to new cache object. tests may assign a mock cache but by default it is None
 (this will avoid any implicit caching behavior confusing unit tests)

---
 lib/spack/llnl/util/filesystem.py          |  9 +++++++++
 lib/spack/spack/__init__.py                |  5 ++++-
 lib/spack/spack/cmd/test.py                |  4 +---
 lib/spack/spack/stage.py                   |  4 +---
 lib/spack/spack/test/mock_packages_test.py | 12 +++++++++---
 5 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/lib/spack/llnl/util/filesystem.py b/lib/spack/llnl/util/filesystem.py
index c4665c284cf..7586d514d1d 100644
--- a/lib/spack/llnl/util/filesystem.py
+++ b/lib/spack/llnl/util/filesystem.py
@@ -392,3 +392,12 @@ def remove_linked_tree(path):
             os.unlink(path)
         else:
             shutil.rmtree(path, True)
+
+class FsCache(object):
+    def __init__(self, root):
+        self.root = os.path.abspath(root)
+
+    def store(self, copyCmd, relativeDst):
+        dst = join_path(self.root, relativeDst)
+        mkdirp(os.path.dirname(dst))
+        copyCmd(dst)
diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index 6fb472b15d9..0041d506243 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -47,7 +47,10 @@
 repos_path     = join_path(var_path, "repos")
 share_path     = join_path(spack_root, "share", "spack")
 cache_path     = join_path(var_path, "cache")
-mkdirp(cache_path)
+
+# TODO: i get a complaint if i dont qualify this, fix that
+import llnl.util.filesystem
+cache = llnl.util.filesystem.FsCache(cache_path)
 
 prefix = spack_root
 opt_path       = join_path(prefix, "opt")
diff --git a/lib/spack/spack/cmd/test.py b/lib/spack/spack/cmd/test.py
index 233cd186f09..1a025218146 100644
--- a/lib/spack/spack/cmd/test.py
+++ b/lib/spack/spack/cmd/test.py
@@ -67,7 +67,5 @@ def test(parser, args):
             
             if not os.path.exists(outputDir):
                 mkdirp(outputDir)
-        spack.cache_path = join_path(spack.var_path, "test-cache")
-        mkdirp(spack.cache_path)
+        spack.cache = None
         spack.test.run(args.names, outputDir, args.verbose)
-        shutil.rmtree(spack.cache_path, ignore_errors=True)
diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index 54359bddce2..780f391603f 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -322,9 +322,7 @@ def check(self):
 
 
     def cache_local(self):
-        archiveDst = join_path(os.path.abspath(spack.cache_path), self.mirror_path)
-        mkdirp(os.path.dirname(archiveDst))
-        self.fetcher.archive(archiveDst)
+        spack.cache.store(self.fetcher.archive, self.mirror_path)
 
 
     def expand_archive(self):
diff --git a/lib/spack/spack/test/mock_packages_test.py b/lib/spack/spack/test/mock_packages_test.py
index 85c15d4a6ad..06d7e7d4e14 100644
--- a/lib/spack/spack/test/mock_packages_test.py
+++ b/lib/spack/spack/test/mock_packages_test.py
@@ -34,6 +34,8 @@
 from spack.repository import RepoPath
 from spack.spec import Spec
 
+import llnl.util.tty as tty
+
 mock_compiler_config = """\
 compilers:
   all:
@@ -130,11 +132,15 @@ def rm_cache(self):
 
 
     def setUp(self):
-        self.rm_cache()
-        mkdirp(spack.cache_path)
+        spack.cache = MockCache()
         self.initmock()
 
 
     def tearDown(self):
-        self.rm_cache()
+        spack.cache = None
         self.cleanmock()
+        
+class MockCache(object):
+    def store(self, copyCmd, relativeDst):
+        tty.warn("Copying " + str(relativeDst))
+        pass

From 13bf7d4ff11e6897d4b688c16564f924e40f657e Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Thu, 24 Mar 2016 12:02:39 -0700
Subject: [PATCH 12/25] (1) move definition of MockCache to test command (no
 definitions or extra work is required in MockPackagesTest) (2) removing
 outdated logic (which originated in this branch) and minor cleanup

---
 lib/spack/spack/cmd/test.py                |  7 ++++++-
 lib/spack/spack/test/git_fetch.py          |  1 +
 lib/spack/spack/test/mock_packages_test.py | 13 -------------
 3 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/lib/spack/spack/cmd/test.py b/lib/spack/spack/cmd/test.py
index 1a025218146..3c405c5c6be 100644
--- a/lib/spack/spack/cmd/test.py
+++ b/lib/spack/spack/cmd/test.py
@@ -51,6 +51,11 @@ def setup_parser(subparser):
         help="verbose output")
 
 
+class MockCache(object):
+    def store(self, copyCmd, relativeDst):
+        pass
+
+
 def test(parser, args):
     if args.list:
         print "Available tests:"
@@ -67,5 +72,5 @@ def test(parser, args):
             
             if not os.path.exists(outputDir):
                 mkdirp(outputDir)
-        spack.cache = None
+        spack.cache = MockCache()
         spack.test.run(args.names, outputDir, args.verbose)
diff --git a/lib/spack/spack/test/git_fetch.py b/lib/spack/spack/test/git_fetch.py
index d3e1206c13b..35780441166 100644
--- a/lib/spack/spack/test/git_fetch.py
+++ b/lib/spack/spack/test/git_fetch.py
@@ -30,6 +30,7 @@
 from spack.test.mock_repo import MockGitRepo
 from spack.version import ver
 
+
 class GitFetchTest(MockPackagesTest):
     """Tests fetching from a dummy git repository."""
 
diff --git a/lib/spack/spack/test/mock_packages_test.py b/lib/spack/spack/test/mock_packages_test.py
index 06d7e7d4e14..6d24a84150b 100644
--- a/lib/spack/spack/test/mock_packages_test.py
+++ b/lib/spack/spack/test/mock_packages_test.py
@@ -34,8 +34,6 @@
 from spack.repository import RepoPath
 from spack.spec import Spec
 
-import llnl.util.tty as tty
-
 mock_compiler_config = """\
 compilers:
   all:
@@ -127,20 +125,9 @@ def cleanmock(self):
             pkg.dependencies.update(deps)
 
 
-    def rm_cache(self):
-        shutil.rmtree(spack.cache_path, ignore_errors=True)
-
-
     def setUp(self):
-        spack.cache = MockCache()
         self.initmock()
 
 
     def tearDown(self):
-        spack.cache = None
         self.cleanmock()
-        
-class MockCache(object):
-    def store(self, copyCmd, relativeDst):
-        tty.warn("Copying " + str(relativeDst))
-        pass

From fe71ba992d26b66a4a9492d9b0fbf17b1410b1e1 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Thu, 24 Mar 2016 12:16:50 -0700
Subject: [PATCH 13/25] remove unused import

---
 lib/spack/spack/cmd/test.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/spack/spack/cmd/test.py b/lib/spack/spack/cmd/test.py
index 3c405c5c6be..82bf3928c36 100644
--- a/lib/spack/spack/cmd/test.py
+++ b/lib/spack/spack/cmd/test.py
@@ -23,7 +23,6 @@
 # Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
 import os
-import shutil
 from pprint import pprint
 
 from llnl.util.filesystem import join_path, mkdirp

From 142d1f5cbc098a4e8a0046148400bb2f40e839bc Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Thu, 24 Mar 2016 19:28:21 -0700
Subject: [PATCH 14/25] stage creates cache fetcher with cache object (so it
 can be mocked for tests)

---
 lib/spack/llnl/util/filesystem.py |  9 ---------
 lib/spack/spack/__init__.py       |  4 ++--
 lib/spack/spack/cmd/test.py       | 14 ++++++++++++++
 lib/spack/spack/fetch_strategy.py | 14 ++++++++++++++
 lib/spack/spack/stage.py          |  2 +-
 5 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/lib/spack/llnl/util/filesystem.py b/lib/spack/llnl/util/filesystem.py
index 7586d514d1d..c4665c284cf 100644
--- a/lib/spack/llnl/util/filesystem.py
+++ b/lib/spack/llnl/util/filesystem.py
@@ -392,12 +392,3 @@ def remove_linked_tree(path):
             os.unlink(path)
         else:
             shutil.rmtree(path, True)
-
-class FsCache(object):
-    def __init__(self, root):
-        self.root = os.path.abspath(root)
-
-    def store(self, copyCmd, relativeDst):
-        dst = join_path(self.root, relativeDst)
-        mkdirp(os.path.dirname(dst))
-        copyCmd(dst)
diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index 0041d506243..6e7cb217c82 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -49,8 +49,8 @@
 cache_path     = join_path(var_path, "cache")
 
 # TODO: i get a complaint if i dont qualify this, fix that
-import llnl.util.filesystem
-cache = llnl.util.filesystem.FsCache(cache_path)
+import spack.fetch_strategy
+cache = fetch_strategy.FsCache(cache_path)
 
 prefix = spack_root
 opt_path       = join_path(prefix, "opt")
diff --git a/lib/spack/spack/cmd/test.py b/lib/spack/spack/cmd/test.py
index 82bf3928c36..8c9dea3c666 100644
--- a/lib/spack/spack/cmd/test.py
+++ b/lib/spack/spack/cmd/test.py
@@ -31,6 +31,7 @@
 
 import spack
 import spack.test
+from spack.fetch_strategy import FetchError
 
 description ="Run unit tests"
 
@@ -54,6 +55,19 @@ class MockCache(object):
     def store(self, copyCmd, relativeDst):
         pass
 
+    def fetcher(self, targetPath, digest):
+        return MockCacheFetcher()
+
+
+class MockCacheFetcher(object):
+    def set_stage(self, stage):
+        pass
+    
+    def fetch(self):
+        raise FetchError("Mock cache always fails for tests")
+
+    def __str__(self):
+        return "[mock fetcher]"
 
 def test(parser, args):
     if args.list:
diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index fc5d7e231cf..b696a12e7ad 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -689,6 +689,20 @@ def for_package_version(pkg, version):
     raise InvalidArgsError(pkg, version)
 
 
+class FsCache(object):
+    def __init__(self, root):
+        self.root = os.path.abspath(root)
+
+    def store(self, copyCmd, relativeDst):
+        dst = join_path(self.root, relativeDst)
+        mkdirp(os.path.dirname(dst))
+        copyCmd(dst)
+        
+    def fetcher(self, targetPath, digest):
+        url = "file://" + join_path(self.root, targetPath)
+        return URLFetchStrategy(url, digest)
+
+
 class FetchError(spack.error.SpackError):
     def __init__(self, msg, long_msg=None):
         super(FetchError, self).__init__(msg, long_msg)
diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index 780f391603f..9f2619f43e1 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -273,7 +273,6 @@ def fetch(self, mirror_only=False):
             # the root, so we add a '/' if it is not present.
             mirror_roots = [root if root.endswith('/') else root + '/'
                             for root in mirrors.values()]
-            mirror_roots.append("file://" + os.path.abspath(spack.cache_path) + os.sep)
             urls = [urljoin(root, self.mirror_path) for root in mirror_roots]
 
             # If this archive is normally fetched from a tarball URL,
@@ -290,6 +289,7 @@ def fetch(self, mirror_only=False):
             # Add URL strategies for all the mirrors with the digest
             for url in urls:
                 fetchers.insert(0, fs.URLFetchStrategy(url, digest))
+            fetchers.insert(0, spack.cache.fetcher(self.mirror_path, digest))
 
         for fetcher in fetchers:
             try:

From 6423eab917f6914cfce253315c9063762e6ae749 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Thu, 24 Mar 2016 19:45:10 -0700
Subject: [PATCH 15/25] implemented cache_local method for DIY stage (as a
 noop)

---
 lib/spack/spack/stage.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index 9f2619f43e1..e8239d27bef 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -503,6 +503,8 @@ def destroy(self):
         # No need to destroy DIY stage.
         pass
 
+    def cache_local(self):
+        tty.msg("Sources for DIY stages are not cached")
 
 def _get_mirrors():
     """Get mirrors from spack configuration."""

From bd5abb292254b40140d1b61849cb86851718b335 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Thu, 24 Mar 2016 19:48:15 -0700
Subject: [PATCH 16/25] spacing issue

---
 lib/spack/spack/stage.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index e8239d27bef..d5ee231ef71 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -506,6 +506,7 @@ def destroy(self):
     def cache_local(self):
         tty.msg("Sources for DIY stages are not cached")
 
+
 def _get_mirrors():
     """Get mirrors from spack configuration."""
     config = spack.config.get_config('mirrors')

From 06c98320a88924234a86b038ca7d3a60a8361f8c Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Fri, 25 Mar 2016 18:38:26 -0700
Subject: [PATCH 17/25] handle case where file contents change but resource
 name does not (e.g. if resource maintainer uses same name for each new
 version of a package)

---
 lib/spack/spack/fetch_strategy.py | 10 ++++++++++
 lib/spack/spack/mirror.py         |  5 ++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index b696a12e7ad..9938f011d00 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -107,6 +107,8 @@ def reset(self):   pass  # Revert to freshly downloaded state.
 
     def archive(self, destination): pass  # Used to create tarball for mirror.
 
+    def file_hash(self): pass # Identifies the resource to be retrieved
+
     def __str__(self):  # Should be human readable URL.
         return "FetchStrategy.__str___"
 
@@ -217,6 +219,10 @@ def archive_file(self):
         """Path to the source archive within this stage directory."""
         return self.stage.archive_file
 
+    @property
+    def file_hash(self):
+        return self.digest
+
     @_needs_stage
     def expand(self):
         if not self.expand_archive:
@@ -349,6 +355,10 @@ def archive(self, destination, **kwargs):
         self.stage.chdir()
         tar('-czf', destination, os.path.basename(self.stage.source_path))
 
+    @property
+    def file_hash(self):
+        return None
+
     def __str__(self):
         return "VCS: %s" % self.url
 
diff --git a/lib/spack/spack/mirror.py b/lib/spack/spack/mirror.py
index 6981f69ac0e..cb2588fb290 100644
--- a/lib/spack/spack/mirror.py
+++ b/lib/spack/spack/mirror.py
@@ -61,7 +61,10 @@ def mirror_archive_filename(spec, fetcher):
         # Otherwise we'll make a .tar.gz ourselves
         ext = 'tar.gz'
 
-    filename = "%s-%s" % (spec.package.name, spec.version)
+    tokens = [spec.package.name, spec.version]
+    if fetcher.file_hash:
+        tokens.append(fetcher.file_hash)
+    filename = '-'.join(str(t) for t in tokens)
     if ext:
         filename += ".%s" % ext
     return filename

From bee224c567ee735547bb183cd6a1d6e04309c81a Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Tue, 29 Mar 2016 18:25:22 -0700
Subject: [PATCH 18/25] mirror archive filename now includes the digest type as
 well as the digest

---
 lib/spack/spack/fetch_strategy.py | 10 ----------
 lib/spack/spack/mirror.py         |  7 +++++--
 lib/spack/spack/package.py        |  7 +++++++
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 9938f011d00..b696a12e7ad 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -107,8 +107,6 @@ def reset(self):   pass  # Revert to freshly downloaded state.
 
     def archive(self, destination): pass  # Used to create tarball for mirror.
 
-    def file_hash(self): pass # Identifies the resource to be retrieved
-
     def __str__(self):  # Should be human readable URL.
         return "FetchStrategy.__str___"
 
@@ -219,10 +217,6 @@ def archive_file(self):
         """Path to the source archive within this stage directory."""
         return self.stage.archive_file
 
-    @property
-    def file_hash(self):
-        return self.digest
-
     @_needs_stage
     def expand(self):
         if not self.expand_archive:
@@ -355,10 +349,6 @@ def archive(self, destination, **kwargs):
         self.stage.chdir()
         tar('-czf', destination, os.path.basename(self.stage.source_path))
 
-    @property
-    def file_hash(self):
-        return None
-
     def __str__(self):
         return "VCS: %s" % self.url
 
diff --git a/lib/spack/spack/mirror.py b/lib/spack/spack/mirror.py
index cb2588fb290..c929a092b4f 100644
--- a/lib/spack/spack/mirror.py
+++ b/lib/spack/spack/mirror.py
@@ -62,8 +62,11 @@ def mirror_archive_filename(spec, fetcher):
         ext = 'tar.gz'
 
     tokens = [spec.package.name, spec.version]
-    if fetcher.file_hash:
-        tokens.append(fetcher.file_hash)
+    package = spack.repo.get(spec)
+    digests = package.digests
+    if digests:
+        if 'md5' in digests:
+            tokens.extend(['md5', digests['md5']])
     filename = '-'.join(str(t) for t in tokens)
     if ext:
         filename += ".%s" % ext
diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index d007f37aebb..2feea51fa57 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -397,6 +397,13 @@ def version(self):
             raise ValueError("Can only get of package with concrete version.")
         return self.spec.versions[0]
 
+    @property
+    def digests(self):
+        versionInfo = self.versions[self.version]
+        digests = {}
+        if 'md5' in versionInfo:
+            digests['md5'] = versionInfo['md5']
+        return digests 
 
     @memoized
     def version_urls(self):

From ce4de6227e339bab98f8a73013bce1898f275b6f Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Tue, 29 Mar 2016 18:45:58 -0700
Subject: [PATCH 19/25] (1) access package via spec property (2) use any digest
 to form archive filename

---
 lib/spack/spack/mirror.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/spack/spack/mirror.py b/lib/spack/spack/mirror.py
index c929a092b4f..78db22f73b7 100644
--- a/lib/spack/spack/mirror.py
+++ b/lib/spack/spack/mirror.py
@@ -62,11 +62,11 @@ def mirror_archive_filename(spec, fetcher):
         ext = 'tar.gz'
 
     tokens = [spec.package.name, spec.version]
-    package = spack.repo.get(spec)
-    digests = package.digests
+    digests = spec.package.digests
     if digests:
-        if 'md5' in digests:
-            tokens.extend(['md5', digests['md5']])
+        # If a package has multiple digests, any one is sufficient to identify it
+        digestType, digest = digests.iteritems().next()
+        tokens.extend([digestType, digest])
     filename = '-'.join(str(t) for t in tokens)
     if ext:
         filename += ".%s" % ext

From 03d907e1e5bfc01f7cdb457dbcd58bb903683e34 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Tue, 29 Mar 2016 18:48:25 -0700
Subject: [PATCH 20/25] in the case of multiple digests, avoid creating
 different mirror filenames from run to run (as long as the available digests
 do not change)

---
 lib/spack/spack/mirror.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/spack/spack/mirror.py b/lib/spack/spack/mirror.py
index 78db22f73b7..64f589ad8bf 100644
--- a/lib/spack/spack/mirror.py
+++ b/lib/spack/spack/mirror.py
@@ -65,7 +65,7 @@ def mirror_archive_filename(spec, fetcher):
     digests = spec.package.digests
     if digests:
         # If a package has multiple digests, any one is sufficient to identify it
-        digestType, digest = digests.iteritems().next()
+        digestType, digest = sorted(digests.iteritems())[0]
         tokens.extend([digestType, digest])
     filename = '-'.join(str(t) for t in tokens)
     if ext:

From c40559433bdfadb6059070060114880c9042d799 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Tue, 29 Mar 2016 18:54:24 -0700
Subject: [PATCH 21/25] added docstring

---
 lib/spack/spack/package.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index 2feea51fa57..d1479ec9de7 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -399,6 +399,7 @@ def version(self):
 
     @property
     def digests(self):
+        """All digests for the concretized package version."""
         versionInfo = self.versions[self.version]
         digests = {}
         if 'md5' in versionInfo:

From a0c42a3fd1a8c5319ff8e02313b7f12e8c59349d Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Tue, 29 Mar 2016 18:58:18 -0700
Subject: [PATCH 22/25] removed stale TODO

---
 lib/spack/spack/__init__.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index 6e7cb217c82..a2d61fa2f71 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -48,9 +48,8 @@
 share_path     = join_path(spack_root, "share", "spack")
 cache_path     = join_path(var_path, "cache")
 
-# TODO: i get a complaint if i dont qualify this, fix that
 import spack.fetch_strategy
-cache = fetch_strategy.FsCache(cache_path)
+cache = spack.fetch_strategy.FsCache(cache_path)
 
 prefix = spack_root
 opt_path       = join_path(prefix, "opt")

From de1ec4be8b0c7bc8c36e88a460e64b3be38cff35 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Mon, 6 Jun 2016 12:26:13 -0700
Subject: [PATCH 23/25] change source archive caching to omit digest from name
 and instead calculate and compare the checksum. This achieves the original
 goal of discarding stale cache files without preserving multiple files for
 the same version.

---
 lib/spack/spack/fetch_strategy.py | 23 +++++++++++++++++++++--
 lib/spack/spack/mirror.py         |  8 +-------
 lib/spack/spack/package.py        |  9 ---------
 3 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 4bbf7bb34c8..fde2a8805e4 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -343,7 +343,7 @@ def reset(self):
 
     def __repr__(self):
         url = self.url if self.url else "no url"
-        return "URLFetchStrategy<%s>" % url
+        return "%s<%s>" % (self.__class__.__name__, url)
 
     def __str__(self):
         if self.url:
@@ -352,6 +352,25 @@ def __str__(self):
             return "[no url]"
 
 
+class URLMirrorFetchStrategy(URLFetchStrategy):
+    """The resource associated with a URL at a mirror may be out of date.
+    """
+    def __init__(self, *args, **kwargs):
+        super(URLMirrorFetchStrategy, self).__init__(*args, **kwargs)
+    
+    @_needs_stage
+    def fetch(self):
+        super(URLMirrorFetchStrategy, self).fetch()
+        if self.digest:
+            try:
+                self.check()
+            except ChecksumError:
+                # Future fetchers will assume they don't need to download if the
+                # file remains
+                os.remove(self.archive_file)
+                raise
+
+
 class VCSFetchStrategy(FetchStrategy):
     def __init__(self, name, *rev_types, **kwargs):
         super(VCSFetchStrategy, self).__init__()
@@ -816,7 +835,7 @@ def store(self, copyCmd, relativeDst):
         
     def fetcher(self, targetPath, digest):
         url = "file://" + join_path(self.root, targetPath)
-        return URLFetchStrategy(url, digest)
+        return URLMirrorFetchStrategy(url, digest)
 
 
 class FetchError(spack.error.SpackError):
diff --git a/lib/spack/spack/mirror.py b/lib/spack/spack/mirror.py
index 81a2f6afb77..0bbcfba6b4f 100644
--- a/lib/spack/spack/mirror.py
+++ b/lib/spack/spack/mirror.py
@@ -61,13 +61,7 @@ def mirror_archive_filename(spec, fetcher):
         # Otherwise we'll make a .tar.gz ourselves
         ext = 'tar.gz'
 
-    tokens = [spec.package.name, spec.version]
-    digests = spec.package.digests
-    if digests:
-        # If a package has multiple digests, any one is sufficient to identify it
-        digestType, digest = sorted(digests.iteritems())[0]
-        tokens.extend([digestType, digest])
-    filename = '-'.join(str(t) for t in tokens)
+    filename = "%s-%s" % (spec.package.name, spec.version)
     if ext:
         filename += ".%s" % ext
     return filename
diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index 70ec243726b..cbf50e56f60 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -413,15 +413,6 @@ def version(self):
             raise ValueError("Can only get of package with concrete version.")
         return self.spec.versions[0]
 
-    @property
-    def digests(self):
-        """All digests for the concretized package version."""
-        versionInfo = self.versions[self.version]
-        digests = {}
-        if 'md5' in versionInfo:
-            digests['md5'] = versionInfo['md5']
-        return digests 
-
     @memoized
     def version_urls(self):
         """Return a list of URLs for different versions of this

From a2754894ea67e0e751121411ff92d60ca68ab089 Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Tue, 7 Jun 2016 16:26:54 -0700
Subject: [PATCH 24/25] (1) FsCache store now takes a fetcher vs. just a copy
 command (2) use [1] to conditionally cache resource: only save it if there is
 a feature which identifies it uniquely (for example do not cache a repository
 if it pulls the latest state vs. a particular tag/commit)

---
 lib/spack/spack/fetch_strategy.py | 16 ++++++++++++++--
 lib/spack/spack/stage.py          |  2 +-
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index fde2a8805e4..3221716b91c 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -828,10 +828,22 @@ class FsCache(object):
     def __init__(self, root):
         self.root = os.path.abspath(root)
 
-    def store(self, copyCmd, relativeDst):
+    def store(self, fetcher, relativeDst):
+        unique = False
+        uidGroups = [['tag', 'commit'], ['digest'], ['revision']]
+        for grp in uidGroups:
+            try:
+                unique |= any(getattr(fetcher, x) for x in grp)
+            except AttributeError:
+                pass
+            if unique:
+                break
+        if not unique:
+            return
+
         dst = join_path(self.root, relativeDst)
         mkdirp(os.path.dirname(dst))
-        copyCmd(dst)
+        fetcher.archive(dst)
         
     def fetcher(self, targetPath, digest):
         url = "file://" + join_path(self.root, targetPath)
diff --git a/lib/spack/spack/stage.py b/lib/spack/spack/stage.py
index f28934d10ab..b08cce43b8b 100644
--- a/lib/spack/spack/stage.py
+++ b/lib/spack/spack/stage.py
@@ -337,7 +337,7 @@ def check(self):
 
 
     def cache_local(self):
-        spack.cache.store(self.fetcher.archive, self.mirror_path)
+        spack.cache.store(self.fetcher, self.mirror_path)
 
 
     def expand_archive(self):

From 3b71d78f3cddeb1b622b9a49146adadbd1b1d9dc Mon Sep 17 00:00:00 2001
From: Peter Scheibel <scheibel1@llnl.gov>
Date: Wed, 8 Jun 2016 09:57:56 -0700
Subject: [PATCH 25/25] rename URLMirrorFetchStrategy to CacheURLFetchStrategy
 since it isnt used to manage all mirror URLs - just the cache (the specific
 behavior that a URL may refer to a stale resource doesn't necessarily apply
 to mirrors)

---
 lib/spack/spack/fetch_strategy.py | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 3221716b91c..2607d0a7f40 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -352,15 +352,14 @@ def __str__(self):
             return "[no url]"
 
 
-class URLMirrorFetchStrategy(URLFetchStrategy):
-    """The resource associated with a URL at a mirror may be out of date.
-    """
+class CacheURLFetchStrategy(URLFetchStrategy):
+    """The resource associated with a cache URL may be out of date."""
     def __init__(self, *args, **kwargs):
-        super(URLMirrorFetchStrategy, self).__init__(*args, **kwargs)
+        super(CacheURLFetchStrategy, self).__init__(*args, **kwargs)
     
     @_needs_stage
     def fetch(self):
-        super(URLMirrorFetchStrategy, self).fetch()
+        super(CacheURLFetchStrategy, self).fetch()
         if self.digest:
             try:
                 self.check()
@@ -847,7 +846,7 @@ def store(self, fetcher, relativeDst):
         
     def fetcher(self, targetPath, digest):
         url = "file://" + join_path(self.root, targetPath)
-        return URLMirrorFetchStrategy(url, digest)
+        return CacheURLFetchStrategy(url, digest)
 
 
 class FetchError(spack.error.SpackError):