[PATCH] git-version-gen: Fix for tags containing '-'

[Markus Armbruster]

Really old versions of git-describe (before v1.5.0, Feb 2007) don't
have the number of commits in their long format output, i.e. where
modern 'git describe --abbrev=4 --match="v*"' prints
"v0.1-1494-g124b9", they print "v0.1-1494-g124b9". git-version-gen
recognizes both patterns, and normalizes the old format to the new
one.

Unfortunately, this normalization code gets confused when the tag
contains '-'. Reproducer:

$ git-tag -m test v0.2-rc1
$ build-aux/git-version-gen .tarball-version; echo
build-aux/git-version-gen: WARNING: git rev-list failed
UNKNOWN

We take exact tag "v0.2-rc1" for the old format, extract the presumed
tag "v0.2" from it, then run "git rev-list v0.2..HEAD" to count
commits since tha tag. Fails, because tag "v0.2" does not exist.

We could perhaps drop support for versions from more than a decade
ago. But tightening the pattern match is easy enough, so do that.
Still breaks when you use version tags ending in something matching
-g????, but you arguably get what you deserve then.

Signed-off-by: Markus Armbruster <***@pond.sub.org>
---
build-aux/git-version-gen | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/build-aux/git-version-gen b/build-aux/git-version-gen
index 079849d..6c054b4 100755
--- a/build-aux/git-version-gen
+++ b/build-aux/git-version-gen
@@ -1,6 +1,6 @@
#!/bin/sh
# Print a version string.
-scriptversion=2017-01-09.19; # UTC
+scriptversion=2017-08-06.05; # UTC

# Copyright (C) 2007-2017 Free Software Foundation, Inc.
#
@@ -168,8 +168,8 @@ then
# Newer: v6.10-77-g0f8faeb
# Older: v6.10-g0f8faeb
case $v in
- *-*-*) : git describe is okay three part flavor ;;
- *-*)
+ *-*-g????) : git describe is okay three part flavor ;;
+ *-g????)
: git describe is older two part flavor
# Recreate the number of commits and rewrite such that the
# result is the same as if we were using the newer version

[Jim Meyering]

Post by Markus Armbruster
Really old versions of git-describe (before v1.5.0, Feb 2007) don't
have the number of commits in their long format output, i.e. where
modern 'git describe --abbrev=4 --match="v*"' prints
"v0.1-1494-g124b9", they print "v0.1-1494-g124b9". git-version-gen
recognizes both patterns, and normalizes the old format to the new
one.
Unfortunately, this normalization code gets confused when the tag
$ git-tag -m test v0.2-rc1
$ build-aux/git-version-gen .tarball-version; echo
build-aux/git-version-gen: WARNING: git rev-list failed
UNKNOWN
We take exact tag "v0.2-rc1" for the old format, extract the presumed
tag "v0.2" from it, then run "git rev-list v0.2..HEAD" to count
commits since tha tag. Fails, because tag "v0.2" does not exist.
We could perhaps drop support for versions from more than a decade
ago. But tightening the pattern match is easy enough, so do that.
Still breaks when you use version tags ending in something matching
-g????, but you arguably get what you deserve then.

Hi Markus!

Thank you for that patch.
I've tweaked the commit log, copied it into the ChangeLog file and pushed.

[Paul Eggert]

Thanks for reporting the problem. Unfortunately that patch didn't work for me,
since Git sometimes outputs more than 4 hex digits after the "g", if needed to
avoid ambiguity. Please try the attached further patch, which I installed.

[Jim Meyering]

Post by Paul Eggert
Thanks for reporting the problem. Unfortunately that patch didn't work for
me, since Git sometimes outputs more than 4 hex digits after the "g", if
needed to avoid ambiguity. Please try the attached further patch, which I
installed.

Thanks for the quick fix.

[Markus Armbruster]

Post by Paul Eggert
Thanks for reporting the problem. Unfortunately that patch didn't work
for me, since Git sometimes outputs more than 4 hex digits after the
"g", if needed to avoid ambiguity. Please try the attached further
patch, which I installed.

You're right. Your incremental patch works for me. The pattern could
be tightened, but I figure it's good enough as is.

Hmm, there's an additional problem my patch fails to address:

# Change the first '-' to a '.', so version-comparing tools work properly.
# Remove the "g" in git describe's output string, to save a byte.
v=`echo "$v" | sed 's/-/./;s/\(.*\)-g/\1-/'`;

Messes with '-' in tags. I think it should replace the first '-g'
instead. What do you think?

[Paul Eggert]

Post by Markus Armbruster
# Change the first '-' to a '.', so version-comparing tools work properly.
# Remove the "g" in git describe's output string, to save a byte.
v=`echo "$v" | sed 's/-/./;s/\(.*\)-g/\1-/'`;
Messes with '-' in tags. I think it should replace the first '-g'
instead. What do you think?

Sorry, I'm not following. Could you give an example of the problem? Evidently
the code is messing with the first "-" and the last "-g" deliberately.

[Markus Armbruster]

Post by Paul Eggert

Post by Markus Armbruster
# Change the first '-' to a '.', so version-comparing tools work properly.
# Remove the "g" in git describe's output string, to save a byte.
v=`echo "$v" | sed 's/-/./;s/\(.*\)-g/\1-/'`;
Messes with '-' in tags. I think it should replace the first '-g'
instead. What do you think?

Sorry, I'm not following. Could you give an example of the problem?
Evidently the code is messing with the first "-" and the last "-g"
deliberately.

I was too terse, and not entirely accurate, sorry. Let me try again.

If I understand this code's intent correctly, it tries to change the "-"
separating the tag from the number of additional commits to ".", and the
"-g" separating the number of additional commits from the abbreviated
object name to just "-". Example:

v0.1-1496-gcbc7002

becomes

v0.1.1496-cbc7002

The problem is once again tag names containing "-", because then the
first "-" is *not* the one we want to change.

Example:

$ git-tag -m test v0.2-rc1 HEAD^
$ git-describe
v0.2-rc1-1-gcbc7002
$ build-aux/git-version-gen .tarball-version; echo
0.2.rc1-1-cbc700

We change the tag name instead of the "-" seperating it from the number
of commits.

After the next commit, we'll get "0.2.rc1-2-cbc700". Will those two
version-compare correctly?

Example:

$ git-tag -fm test v0.2-rc1
Updated tag 'v0.2-rc1' (was 1657134)
$ git-describe
v0.2-rc1
$ build-aux/git-version-gen .tarball-version; echo
0.2.rc1

There is no number of commits to change. We change the tag name
instead.

Should we replace /-([^-]+)-g([^-]*)$/ by /.\1-\2/? Extended regexp
for clarity. Tighter matching would be possible, say
/-([0-9]+)-g[0-9a-f]{4,}$/.

[Paul Eggert]

Post by Markus Armbruster
Should we replace /-([^-]+)-g([^-]*)$/ by /.\1-\2/? Extended regexp
for clarity. Tighter matching would be possible, say
/-([0-9]+)-g[0-9a-f]{4,}$/.

Sounds good, I installed the attached.

[Markus Armbruster]

Post by Paul Eggert

Post by Markus Armbruster
Should we replace /-([^-]+)-g([^-]*)$/ by /.\1-\2/? Extended regexp
for clarity. Tighter matching would be possible, say
/-([0-9]+)-g[0-9a-f]{4,}$/.

Sounds good, I installed the attached.

Works for me, thanks!