[PATCH] bisect: visualize with git-log if gitk is unavailable

[Jeff King <peff@peff.net>]

If gitk is not available in the PATH, bisect ends up
exiting with the shell's 127 error code, confusing the git
wrapper into thinking that bisect is not a git command.

We already fallback to git-log if there doesn't seem to be a
graphical display available. We should do the same if gitk
is not available in our PATH at all. This not only fixes the
ugly error message, but is a much more sensible default than
failing to show the user anything.

Reported by Maxin John.

Tested-by: Maxin B. John <maxin@maxinbjohn.info>
Signed-off-by: Jeff King <peff@peff.net>
---
 git-bisect.sh |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/git-bisect.sh b/git-bisect.sh
index c21e33c..415a8d0 100755
--- a/git-bisect.sh
+++ b/git-bisect.sh
@@ -288,10 +288,12 @@ bisect_visualize() {
 
 	if test $# = 0
 	then
-		case "${DISPLAY+set}${SESSIONNAME+set}${MSYSTEM+set}${SECURITYSESSIONID+set}" in
-		'')	set git log ;;
-		set*)	set gitk ;;
-		esac
+		if test -n "${DISPLAY+set}${SESSIONNAME+set}${MSYSTEM+set}${SECURITYSESSIONID+set}" &&
+		   type gitk >/dev/null 2>&1; then
+			set gitk
+		else
+			set git log
+		fi
 	else
 		case "$1" in
 		git*|tig) ;;
-- 
1.7.2.5.22.g853c5