git-svn: Demonstrate a bug with root commits in mergeinfo ranges

If a svn:mergeinfo range starts at a commit that was converted as a
git root commit (e.g., r1 or a branch that was created out of thin
air), then there is an error when git-svn tries to run

    git rev-list "$bottom_commit^..$top_commit"

because $bottom_commit (the git commit corresponding to r1) has no
parent.

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

t/t9159-git-svn-no-parent-mergeinfo.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+test_description='git svn handling of root commits in merge ranges'
+. ./lib-git-svn.sh
+
+test_expect_failure 'test handling of root commits in merge ranges' '
+	mkdir -p init/trunk init/branches init/tags &&
+	echo "r1" > init/trunk/file.txt &&
+	svn_cmd import -m "initial import" init "$svnrepo" &&
+	svn_cmd co "$svnrepo" tmp &&
+	(
+		cd tmp &&
+		echo "r2" > trunk/file.txt &&
+		svn_cmd commit -m "Modify file.txt on trunk" &&
+		svn_cmd cp trunk@1 branches/a &&
+		svn_cmd commit -m "Create branch a from trunk r1" &&
+		svn_cmd propset svn:mergeinfo /trunk:1-2 branches/a &&
+		svn_cmd commit -m "Fake merge of trunk r2 into branch a" &&
+		mkdir branches/b &&
+		echo "r5" > branches/b/file2.txt &&
+		svn_cmd add branches/b &&
+		svn_cmd commit -m "Create branch b from thin air" &&
+		echo "r6" > branches/b/file2.txt &&
+		svn_cmd commit -m "Modify file2.txt on branch b" &&
+		svn_cmd cp branches/b@5 branches/c &&
+		svn_cmd commit -m "Create branch c from branch b r5" &&
+		svn_cmd propset svn:mergeinfo /branches/b:5-6 branches/c &&
+		svn_cmd commit -m "Fake merge of branch b r6 into branch c"
+	) &&
+	git svn init -s "$svnrepo" &&
+	git svn fetch
+	'
+
+test_done