From 892dd4d97fb2d476b24b280279cbdadcfeb0d19c Mon Sep 17 00:00:00 2001
From: Gregory Becker <becker33@llnl.gov>
Date: Fri, 22 Jan 2021 18:16:30 -0800
Subject: [PATCH] add `spack checkout` command

---
 lib/spack/spack/cmd/checkout.py | 78 +++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 lib/spack/spack/cmd/checkout.py

diff --git a/lib/spack/spack/cmd/checkout.py b/lib/spack/spack/cmd/checkout.py
new file mode 100644
index 00000000000..c368415ec50
--- /dev/null
+++ b/lib/spack/spack/cmd/checkout.py
@@ -0,0 +1,78 @@
+# Copyright 2013-2021 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+import sys
+
+import llnl.util.tty as tty
+from spack.util.executable import ProcessError, which
+
+_SPACK_UPSTREAM = 'https://github.com/spack/spack'
+
+description = "update the spack prefix to a git ref"
+section = "admin"
+level = "long"
+
+git = None
+
+def setup_parser(subparser):
+    subparser.add_argument(
+        '-r', '--remote', action='store', default='origin',
+        help="name of the git remote from which to fetch")
+    subparser.add_argument(
+        '--url', action='store', default=None,
+        help="url to use if the remote does not already exist")
+    subparser.add_argument(
+        'ref', help="git reference to checkout")
+
+
+def fetch_remote(remote, url):
+    # Ensure we have the appropriate remote configured
+    remotes = git('remote', output=str, errror=str).split('\n')
+    if remote in remotes:
+        remote_url = git('remote', 'get-url', remote, output=str, error=str)
+        remote_url = remote_url.strip('\n')
+        if url and remote_url != url:
+            msg = "Git url %s does not match given url %s" % (remote_url, url)
+            msg += " for remote '%s'. Either use the git url or" % remote
+            msg += " specify a new remote name for the new url."
+            tty.die(msg)
+    elif not url:
+        msg = "Spack requires url to checkout from unknown remote %s" % remote
+        tty.die(msg)
+    else:
+        git('remote', 'add', remote, url)
+    git('fetch', remote)
+
+
+def known_commit_or_tag(ref):
+    # No need to fetch for tags and commits if we have the ref already
+    # Fetch on other types rather than failing here because a tree ref could
+    # be ambiguous with a commit ref after fetching
+    ref_type = git('cat-file', '-t', ref,
+                   output=str, error=str, fail_on_error=False).strip('\n ')
+    return ref_type in ('commit', 'tag')
+
+
+def checkout(parser, args):
+    deployment_required_args = {'remote': 'origin'}
+    deployment.setup_deployment_args('checkout', args,
+                                     deployment_required_args)
+
+    remote = args.remote or origin
+    url = args.url
+    ref = args.ref
+
+    global git  # make git available to called methods
+    git = which('git', required=True)
+
+    # Always fetch branches
+    branches = map(lambda b: b.strip('* '),
+                   git('branch', output=str, error=str).split('\n'))
+    if ref in branches or not known_commit_or_tag(ref):
+        fetch_remote(remote, url)
+
+    # For branches, ensure we're getting the version from the correct remote
+    full_ref = '%s/%s' % (remote, ref) if ref in branches else ref
+    git('checkout', full_ref)