optimize instantiation and comparison of versions (#29429)

Re-work the checks and comparisons around commit versions, when no
commit version is involved the overhead is now in the noise, where one
is the overhead is now constant rather than linear.

lib/spack/spack/version.py

@@ -48,7 +48,7 @@
 VALID_VERSION = re.compile(r'^[A-Za-z0-9_.-]+$')
 
 # regex for a commit version
-COMMIT_VERSION = re.compile(r'^[a-z0-9]{40}$')
+COMMIT_VERSION = re.compile(r'^[a-f0-9]{40}$')
 
 # regex for version segments
 SEGMENT_REGEX = re.compile(r'(?:(?P<num>[0-9]+)|(?P<str>[a-zA-Z]+))(?P<sep>[_.-]*)')
@@ -167,7 +167,14 @@ def __gt__(self, other):
 
 class Version(object):
     """Class to represent versions"""
-    __slots__ = ['version', 'separators', 'string', 'is_commit', 'commit_lookup']
+    __slots__ = [
+        "version",
+        "separators",
+        "string",
+        "commit_lookup",
+        "is_commit",
+        "commit_version",
+    ]
 
     def __init__(self, string):
         if not isinstance(string, str):
@@ -182,7 +189,7 @@ def __init__(self, string):
 
         # An object that can lookup git commits to compare them to versions
         self.commit_lookup = None
-
+        self.commit_version = None
         segments = SEGMENT_REGEX.findall(string)
         self.version = tuple(
             int(m[0]) if m[0] else VersionStrComponent(m[1]) for m in segments
@@ -195,6 +202,8 @@ def _cmp(self, other_lookups=None):
         commit_lookup = self.commit_lookup or other_lookups
 
         if self.is_commit and commit_lookup:
+            if self.commit_version is not None:
+                return self.commit_version
             commit_info = commit_lookup.get(self.string)
             if commit_info:
                 prev_version, distance = commit_info
@@ -203,7 +212,8 @@ def _cmp(self, other_lookups=None):
                 # If commit is exactly a known version, no distance suffix
                 prev_tuple = Version(prev_version).version if prev_version else ()
                 dist_suffix = (VersionStrComponent(''), distance) if distance else ()
-                return prev_tuple + dist_suffix
+                self.commit_version = prev_tuple + dist_suffix
+                return self.commit_version
 
         return self.version