Re: [PATCH 2/2] cvsserver: Fix for histories with multiple roots

[Junio C Hamano <gitster@pobox.com>]

Steffen Prohaska <prohaska@zib.de> writes:

> Git histories may have multiple roots, which can cause
> git merge-base to fail and this caused git cvsserver to die.
>
> This commit teaches git cvsserver to handle a failing git
> merge-base gracefully, and modifies the test case to verify this.
> All the test cases now use a history with two roots.
>
> Signed-off-by: Steffen Prohaska <prohaska@zib.de>
> ---
>  git-cvsserver.perl              |    5 +++++
>  t/t9400-git-cvsserver-server.sh |   10 +++++++++-
>  2 files changed, 14 insertions(+), 1 deletions(-)
>
> diff --git a/git-cvsserver.perl b/git-cvsserver.perl
> index ecded3b..534b41e 100755
> --- a/git-cvsserver.perl
> +++ b/git-cvsserver.perl
> @@ -2543,6 +2543,11 @@ sub update
>                      if ($parent eq $lastpicked) {
>                          next;
>                      }
> +                    # or it may fail to find a merge base.  In this
> +                    # case we just ignore this merge.
> +                    if (system("git merge-base $lastpicked $parent >/dev/null 2>/dev/null")) {
> +                        next;
> +                    }
>                      my $base = safe_pipe_capture('git-merge-base',
>  						 $lastpicked, $parent);
>                      chomp $base;

That is a "Yes, but..." patch.

Running merge-base always twice, due to fear of uncommon case of
failure, feels quite backwards.

Doesn't this work equally well without running a rather
expensive merge-base twice?

 git-cvsserver.perl |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/git-cvsserver.perl b/git-cvsserver.perl
index ecded3b..afe3d0b 100755
--- a/git-cvsserver.perl
+++ b/git-cvsserver.perl
@@ -2543,8 +2543,15 @@ sub update
                     if ($parent eq $lastpicked) {
                         next;
                     }
-                    my $base = safe_pipe_capture('git-merge-base',
+		    my $base = eval {
+			    safe_pipe_capture('git-merge-base',
 						 $lastpicked, $parent);
+		    };
+		    # The two branches may not be related at all,
+		    # in which case merge base simply fails to find
+		    # any, but that's Ok.
+		    next if ($@);
+
                     chomp $base;
                     if ($base) {
                         my @merged;