git-bisect visualize: work in non-windowed environments better

This teaches "git bisect visualize" to be more useful in non-windowed
environments.

 (1) When no option is given, and $DISPLAY is set, it continues to
     spawn gitk as before;

 (2) When no option is given, and $DISPLAY is unset, "git log" is run
     to show the range of commits between the bad one and the good ones;

 (3) If only "-flag" options are given, "git log <options>" is run.
     E.g. "git bisect visualize --stat"

 (4) Otherwise, all of the given options are taken as the initial part
     of the command line and the commit range expression is given to
     that command.  E.g. "git bisect visualize tig" will run "tig"
     history viewer to show between the bad one and the good ones.

As "visualize" is a bit too long to type, we also give it a shorter
synonym "view".

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-bisect.txt

@@ -92,7 +92,16 @@ During the bisection process, you can say
 $ git bisect visualize
 ------------
 
-to see the currently remaining suspects in `gitk`.
+to see the currently remaining suspects in `gitk`.  `visualize` is a bit
+too long to type and `view` is provided as a synonym.
+
+If `DISPLAY` environment variable is not set, `git log` is used
+instead.  You can even give command line options such as `-p` and
+`--stat`.
+
+------------
+$ git bisect view --stat
+------------
 
 Bisect log and bisect replay
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

git-bisect.sh

@@ -324,8 +324,23 @@ bisect_next() {
 
 bisect_visualize() {
 	bisect_next_check fail
+
+	if test $# = 0
+	then
+		case "${DISPLAY+set}" in
+		'')	set git log ;;
+		set)	set gitk ;;
+		esac
+	else
+		case "$1" in
+		git*|tig) ;;
+		-*)	set git log "$@" ;;
+		*)	set git "$@" ;;
+		esac
+	fi
+
 	not=$(git for-each-ref --format='%(refname)' "refs/bisect/good-*")
-	eval gitk refs/bisect/bad --not $not -- $(cat "$GIT_DIR/BISECT_NAMES")
+	eval '"$@"' refs/bisect/bad --not $not -- $(cat "$GIT_DIR/BISECT_NAMES")
 }
 
 bisect_reset() {
@@ -449,7 +464,7 @@ case "$#" in
     next)
         # Not sure we want "next" at the UI level anymore.
         bisect_next "$@" ;;
-    visualize)
+    visualize|view)
 	bisect_visualize "$@" ;;
     reset)
         bisect_reset "$@" ;;