Re: Fetch from existing gnulib Git repository if needed

[Bruno Haible]

Hi Markus,

> GNU Octave uses Mercurial as the VCS of its main repository.
> Developers are using the bootstrap script of gnulib to automatically clone 
> its Git repository in a subdirectory of Octave's source tree. The revision 
> that we'd like to use is set in the bootstrap.conf script. Currently, that is
> 
> : ${GNULIB_REVISION=d4ec02b3cc70cddaaa5183cc5a45814e0afb2292}
> 
> 
> This is working perfectly for a fresh clone of Octave's source tree. However, 
> when we update GNULIB_REVISION to a newer revision and a user/developer ran 
> the bootstrap script before, running the bootstrap script again fails with an 
> error like the following:
> 
> ./bootstrap: Bootstrapping from checked-out octave sources...
> fatal: reference is not a tree: d4ec02b3cc70cddaaa5183cc5a45814e0afb2292
> program finished with exit code 128

I see. Indeed there is no 'git fetch' in the code branch that you are
highlighting.

> As a workaround we are applying the attached patch to the 
> bootstrap-funclib.sh script to automatically fetch from the remote gnulib 
> repository if the GNULIB_REVISION isn't found in the local gnulib Git 
> repository.

Thanks for the patch. But note that GNULIB_REVISION can hold either a commit
hash or the name of a branch (such as 'stable-202401'). So, we have 4 cases:
  (a) a commit hash, already present
  (b) a commit hash, not known
  (c) a branch, already present
  (d) a branch, not known

The command 'git cat-file commit $GNULIB_REVISION' returns true in the cases
(a) and (c). So, your patch would trigger a 'git fetch' in the cases (b) and
(d). But in case (d), the 'git fetch' is useless:
'git cat-file commit $GNULIB_REVISION' would still fail afterwards.

One can distinguish the four cases in more detail using the commands
  git rev-list --quiet $GNULIB_REVISION --
which tests for case (a) and
  git show-ref --verify --quiet refs/heads/$GNULIB_REVISION
which tests for case (c). This would allow us to do 'git fetch' only in case
(b).

However, I believe the patch below is simpler and achieves the same goal.


2024-04-27  Bruno Haible  <bruno@clisp.org>

        bootstrap: Support checking out a recent GNULIB_REVISION.
        Reported by Markus Mützel <markus.muetzel@gmx.de> in
        <https://lists.gnu.org/archive/html/bug-gnulib/2024-04/msg00462.html>.
        * top/bootstrap-funclib.sh (prepare_GNULIB_SRCDIR): If the
        'git checkout' command fails, fetch the newer commits and then retry it.
        * build-aux/bootstrap: Regenerated.

diff --git a/top/bootstrap-funclib.sh b/top/bootstrap-funclib.sh
index 7511d62d9b..620006d320 100644
--- a/top/bootstrap-funclib.sh
+++ b/top/bootstrap-funclib.sh
@@ -1,6 +1,6 @@
 # A library of shell functions for autopull.sh, autogen.sh, and bootstrap.
 
-scriptlibversion=2024-04-13.15; # UTC
+scriptlibversion=2024-04-27.17; # UTC
 
 # Copyright (C) 2003-2024 Free Software Foundation, Inc.
 #
@@ -462,7 +462,17 @@ prepare_GNULIB_SRCDIR ()
       || die "Error: --gnulib-srcdir or \$GNULIB_SRCDIR is specified," \
              "but does not contain gnulib-tool"
     if test -n "$GNULIB_REVISION" && $use_git; then
-      (cd "$GNULIB_SRCDIR" && git checkout "$GNULIB_REVISION") || exit $?
+      # The 'git checkout "$GNULIB_REVISION"' command succeeds if the
+      # GNULIB_REVISION is a commit hash that exists locally, or if it is
+      # branch name that can be fetched from origin. It fails, however,
+      # if the GNULIB_REVISION is a commit hash that only exists in origin.
+      # In this case, we need a 'git fetch' and then retry
+      # 'git checkout "$GNULIB_REVISION"'.
+      (cd "$GNULIB_SRCDIR" \
+       && { git checkout "$GNULIB_REVISION" 2>/dev/null \
+            || { git fetch origin && git checkout "$GNULIB_REVISION"; }
+          }
+      ) || exit $?
     fi
   else
     if ! $use_git; then