[PATCH] Prevent git blame from segfaulting on a missing author name

[David Reiss <dreiss@facebook.com>]

The author name should never be missing in a valid commit, but
git shouldn't segfault no matter what is in the object database.

Signed-off-by: David Reiss <dreiss@facebook.com>
---
git blame was segfaulting on a repro produced by piping mtn git_export
from the Pidgin repository to git fast-import.  This was the most obvious
fix, but I'm not sure if it is the best solution.

Here's a script that reproduces the segfault.

#!/bin/sh
set -e
git init
echo line > afile
git add afile
TREE=`git write-tree`
cat >badcommit <<EOF
tree $TREE
author <noname> 1234567890 +0000
committer David Reiss <dreiss@facebook.com> 1234567890 +0000

some message
EOF
COMMIT=`git hash-object -t commit -w badcommit`
echo "git --no-pager blame $COMMIT -- afile"
git --no-pager blame $COMMIT -- afile


 builtin-blame.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/builtin-blame.c b/builtin-blame.c
index d4e25a5..5e19c79 100644
--- a/builtin-blame.c
+++ b/builtin-blame.c
@@ -1326,7 +1326,7 @@ static void get_ac_line(const char *inbuf, const char *what,
 	timepos = tmp;
 
 	*tmp = 0;
-	while (*tmp != ' ')
+	while (tmp > person && *tmp != ' ')
 		tmp--;
 	mailpos = tmp + 1;
 	*tmp = 0;
-- 
1.6.3.3