git-svn: Correctly handle root commits in mergeinfo ranges

If the bottom of a mergeinfo range is a commit that maps to a git root
commit, then it doesn't have a parent.  In such a case, use git commit
range "$top_commit" rather than "$bottom_commit^..$top_commit".

[ew: line-wrap at 80 columns]

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Acked-by: Eric Wong <normalperson@yhbt.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/git-svn.perl b/git-svn.perl
index 1f1aa5710..89f83fd27 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -3124,8 +3124,12 @@ sub lookup_svn_merge {
 			next;
 		}
 
-		push @merged_commit_ranges,
-			"$bottom_commit^..$top_commit";
+		if (scalar(command('rev-parse', "$bottom_commit^@"))) {
+			push @merged_commit_ranges,
+			     "$bottom_commit^..$top_commit";
+		} else {
+			push @merged_commit_ranges, "$top_commit";
+		}
 
 		if ( !defined $tip or $top > $tip ) {
 			$tip = $top;