cvsserver: Fix for histories with multiple roots

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              |    9 ++++++++-
 t/t9400-git-cvsserver-server.sh |   10 +++++++++-
 2 files changed, 17 insertions(+), 2 deletions(-)
Signed-off-by: Junio C Hamano <gitster@pobox.com>

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;

t/t9400-git-cvsserver-server.sh

@@ -37,6 +37,13 @@ test_expect_success 'setup' '
   echo >empty &&
   git add empty &&
   git commit -q -m "First Commit" &&
+  mkdir secondroot &&
+  ( cd secondroot &&
+  git init &&
+  touch secondrootfile &&
+  git add secondrootfile &&
+  git commit -m "second root") &&
+  git pull secondroot master &&
   git clone -q --local --bare "$WORKDIR/.git" "$SERVERDIR" >/dev/null 2>&1 &&
   GIT_DIR="$SERVERDIR" git config --bool gitcvs.enabled true &&
   GIT_DIR="$SERVERDIR" git config gitcvs.logfile "$SERVERDIR/gitcvs.log"
@@ -46,7 +53,8 @@ test_expect_success 'setup' '
 # as argument to co -d
 test_expect_success 'basic checkout' \
   'GIT_CONFIG="$git_config" cvs -Q co -d cvswork master &&
-   test "$(echo $(grep -v ^D cvswork/CVS/Entries|cut -d/ -f2,3,5))" = "empty/1.1/"'
+   test "$(echo $(grep -v ^D cvswork/CVS/Entries|cut -d/ -f2,3,5 | head -n 1))" = "empty/1.1/"
+   test "$(echo $(grep -v ^D cvswork/CVS/Entries|cut -d/ -f2,3,5 | tail -n 1))" = "secondrootfile/1.1/"'
 
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