MAINT(snapshot-versions): Change snapshot version format

Until now the snapshot versions looked something like
1.4.0~444~g4afab7c~snapshot. They include the Mumble version which they
are a snapshot for at the beginning, then the revision number (the
amount of commits since the last tag in git's history), followed by the
latest commit's hash (prefixed by "g") and finally the word "snapshot".

The problem with this approach is that it requires knowledge of the git
history at least until the most recent tag. In addition to that it also
requires someone to think about moving the "tag-for-ci" that marks a
release-state in the master branch to be set on every release.

The history requirement is not an issue for a normal clone of the
repository but if someone (e.g. the CI) performs a shallow clone of the
repository, then the script fails.

In order to address this problem, this commit changes the version format
to be 1.4.0~2020-07-02~g4afab7c67~snapshot. The revision number got
replaced by the date of the most recent commit (in ISO format) and the
commit hash is now abbreviated by git itself as it sees fit instead of
manually truncating the commit hash at 7 characters.

That way the script doesn't require knowledge of the latest tag and all
the history after that. That way the script can now be run in a shallow
clone of depth 1.

1 files changed, 33 insertions, 37 deletions

diff --git a/scripts/mumble-version.py b/scripts/mumble-version.py
index 507f643bd..8f23aa035 100755
--- a/scripts/mumble-version.py
+++ b/scripts/mumble-version.py
@@ -11,7 +11,7 @@
 # This is a replacement for `git describe` to make snapshots
 # use the future, untagged version number rather than the previous.
 #
-# The version is of form 1.3.0~154~g4f336a2~snapshot.
+# The version is of form 1.3.0~2020-07-02~g4f336a2~snapshot.
 # It includes the target release version rather than the previous
 # release (as git describe does).
 #
@@ -44,13 +44,16 @@
 # This means that snapshots for Mumble 1.3.0 now have the base version
 # '1.3.0'.
 #
-# It also changes the version string slightly. Instead of using dashes
+# It also changes the version string: Instead of using dashes
 # as a separator in the version string, it now uses tildes. This allows
 # Debian's dpkg version comparer to correctly sort snapshot versions
 # before release versions. The new string also includes 'snapshot' in the
 # version string to denote to users that the given version is a pre-release
-# snapshot. A full new-style version string looks like this:
-# 1.3.0~154~g4f336a2~snapshot.
+# snapshot.
+# Furthermore the version number does use the latest commit's date rather
+# than therevision number since the last tag.
+# A full new-style version string looks like this:
+# 1.3.0~2020-07-02~g4f336a2~snapshot.
 
 from __future__ import (unicode_literals, print_function, division)
 
@@ -92,43 +95,36 @@ def readMumblePriVersion():
 	return version
 
 def main():
-	latestTag = cmd(['git', 'describe', '--abbrev=0', '--tags'])
-	latestTag = strip(latestTag)
-	if len(latestTag) == 0:
-		raise Exception('empty latestTag, unable to continue')
+    # Get all tags associated with the latest commit
+    latestCommitTags = [x for x in cmd(['git', 'tag', '--points-at', 'HEAD']).split("\n") if x]
+    
+    if len(latestCommitTags) > 1:
+        raise RuntimeError("Encountered commit with multiple tags: %s" % latestCommitTags)
 
-	latestCommit = cmd(['git', 'rev-parse', 'HEAD'])
-	if len(latestCommit) < 7:
-		raise Exception('bad commit string: {0}'.format(latestCommit))
-	latestCommit = strip(latestCommit)
+    if len(latestCommitTags) == 1:
+        # Most recent commit is tagged -> this is a tagged release version
+        # Use the tag as the version-string
+        version = latestCommitTags[0]
+    else:
+        # This is a snapshot (i.e. built from a non-tagged commit)
 
-	revListStr = cmd(['git', 'rev-list', '{0}..HEAD'.format(latestTag)])
-	revList = revListStr.split('\n')
-	nrevs = len(revList)-1 # Consider the newline at the end.
-	version = ''
-	if nrevs == 0:
-		# The most recent tag is the latest commit. That means this must
-		# be a tagged release version.
-		# We verify that the tag commit is the current HEAD to make sure it is.
-		revListStr = cmd(['git', 'rev-list', latestTag])
-		revList = revListStr.split('\n')
-		if len(revList) == 0:
-			raise Exception('unable to get rev-list for potential release tag')
-		latestCommitForLatestTag = revList[0]
-		if latestCommitForLatestTag != latestCommit:
-			raise Exception('commit-hash mismatch; aborting potential relase version string')
-		version = latestTag
-	else:
-		mumblePriVersion = readMumblePriVersion()
-		if len(mumblePriVersion) == 0 or not '.' in mumblePriVersion:
-			raise Exception('bad mumblePriVersion: "{0}"'.format(mumblePriVersion))
+        # Get the date of the most recent commit
+        latestCommitDate = cmd(['git', 'log', '-1', '--format=%cd', '--date=short']).strip()
 
-		version = '{0}~{1}~g{2}~snapshot'.format(mumblePriVersion, nrevs, latestCommit[0:7])
+        # Get the hash of the most recent commit (shortened)
+        latestCommitHash = cmd(['git', 'rev-parse', '--short'  , 'HEAD']).strip()
 
-	end = ''
-	if '--newline' in sys.argv:
-		end = None
-	print(version, end=end)
+        # Get the Mumble version that is set in the mumble.pri file
+        mumblePriVersion = readMumblePriVersion()
+        if len(mumblePriVersion) == 0 or not '.' in mumblePriVersion:
+            raise Exception('bad mumblePriVersion: "{0}"'.format(mumblePriVersion))
+
+        version = '{0}~{1}~g{2}~snapshot'.format(mumblePriVersion, latestCommitDate, latestCommitHash)
+
+    end = ''
+    if '--newline' in sys.argv:
+            end = None
+    print(version, end=end)
 
 if __name__ == '__main__':
 	main()