Bisect: teach "bisect start" to optionally use one bad and many good revs.

One bad commit is fundamentally needed for bisect to run,
and if we beforehand know more good commits, we can narrow
the bisect space down without doing the whole tree checkout
every time we give good commits.

This patch implements:

    git bisect start [<bad> [<good>...]] [--] [<pathspec>...]

as a short-hand for this command sequence:

    git bisect start
    git bisect bad $bad
    git bisect good $good1 $good2...

On the other hand, there may be some confusion between revs
(<bad> and <good>...) and <pathspec>... if -- is not used
and if an invalid rev or a pathspec that looks like a rev is
given.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-bisect.sh

@@ -1,15 +1,24 @@
 #!/bin/sh
 
 USAGE='[start|bad|good|next|reset|visualize|replay|log|run]'
-LONG_USAGE='git bisect start [<pathspec>]	reset bisect state and start bisection.
+LONG_USAGE='git bisect start [<bad> [<good>...]] [--] [<pathspec>...]
-git bisect bad [<rev>]		mark <rev> a known-bad revision.
+        reset bisect state and start bisection.
-git bisect good [<rev>...]	mark <rev>... known-good revisions.
+git bisect bad [<rev>]
-git bisect next			find next bisection to test and check it out.
+        mark <rev> a known-bad revision.
-git bisect reset [<branch>]	finish bisection search and go back to branch.
+git bisect good [<rev>...]
-git bisect visualize            show bisect status in gitk.
+        mark <rev>... known-good revisions.
-git bisect replay <logfile>	replay bisection log.
+git bisect next
-git bisect log			show bisect log.
+        find next bisection to test and check it out.
-git bisect run <cmd>... 	use <cmd>... to automatically bisect.'
+git bisect reset [<branch>]
+        finish bisection search and go back to branch.
+git bisect visualize
+        show bisect status in gitk.
+git bisect replay <logfile>
+        replay bisection log.
+git bisect log
+        show bisect log.
+git bisect run <cmd>...
+        use <cmd>... to automatically bisect.'
 
 . git-sh-setup
 require_work_tree
@@ -70,14 +79,48 @@ bisect_start() {
 	#
 	# Get rid of any old bisect state
 	#
-	rm -f "$GIT_DIR/refs/heads/bisect"
+	bisect_clean_state
-	rm -rf "$GIT_DIR/refs/bisect/"
 	mkdir "$GIT_DIR/refs/bisect"
+
+	#
+	# Check for one bad and then some good revisions.
+	#
+	has_double_dash=0
+	for arg; do
+	    case "$arg" in --) has_double_dash=1; break ;; esac
+	done
+	orig_args=$(sq "$@")
+	bad_seen=0
+	while [ $# -gt 0 ]; do
+	    arg="$1"
+	    case "$arg" in
+	    --)
+	        shift
+		break
+		;;
+	    *)
+	        rev=$(git-rev-parse --verify "$arg^{commit}" 2>/dev/null) || {
+		    test $has_double_dash -eq 1 &&
+		        die "'$arg' does not appear to be a valid revision"
+		    break
+		}
+		if [ $bad_seen -eq 0 ]; then
+		    bad_seen=1
+		    bisect_write_bad "$rev"
+		else
+		    bisect_write_good "$rev"
+		fi
+	        shift
+		;;
+	    esac
+        done
+
+	sq "$@" >"$GIT_DIR/BISECT_NAMES"
 	{
 	    printf "git-bisect start"
-	    sq "$@"
+	    echo "$orig_args"
-	} >"$GIT_DIR/BISECT_LOG"
+	} >>"$GIT_DIR/BISECT_LOG"
-	sq "$@" >"$GIT_DIR/BISECT_NAMES"
+	bisect_auto_next
 }
 
 bisect_bad() {
@@ -90,12 +133,17 @@ bisect_bad() {
 	*)
 		usage ;;
 	esac || exit
-	echo "$rev" >"$GIT_DIR/refs/bisect/bad"
+	bisect_write_bad "$rev"
-	echo "# bad: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
 	echo "git-bisect bad $rev" >>"$GIT_DIR/BISECT_LOG"
 	bisect_auto_next
 }
 
+bisect_write_bad() {
+	rev="$1"
+	echo "$rev" >"$GIT_DIR/refs/bisect/bad"
+	echo "# bad: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
+}
+
 bisect_good() {
 	bisect_autostart
         case "$#" in
@@ -106,13 +154,19 @@ bisect_good() {
 	for rev in $revs
 	do
 		rev=$(git-rev-parse --verify "$rev^{commit}") || exit
-		echo "$rev" >"$GIT_DIR/refs/bisect/good-$rev"
+		bisect_write_good "$rev"
-		echo "# good: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
 		echo "git-bisect good $rev" >>"$GIT_DIR/BISECT_LOG"
+
 	done
 	bisect_auto_next
 }
 
+bisect_write_good() {
+	rev="$1"
+	echo "$rev" >"$GIT_DIR/refs/bisect/good-$rev"
+	echo "# good: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
+}
+
 bisect_next_check() {
 	next_ok=no
         test -f "$GIT_DIR/refs/bisect/bad" &&
@@ -190,14 +244,19 @@ bisect_reset() {
 	    usage ;;
 	esac
 	if git checkout "$branch"; then
-		rm -fr "$GIT_DIR/refs/bisect"
+		rm -f "$GIT_DIR/head-name"
-		rm -f "$GIT_DIR/refs/heads/bisect" "$GIT_DIR/head-name"
+		bisect_clean_state
-		rm -f "$GIT_DIR/BISECT_LOG"
-		rm -f "$GIT_DIR/BISECT_NAMES"
-		rm -f "$GIT_DIR/BISECT_RUN"
 	fi
 }
 
+bisect_clean_state() {
+	rm -fr "$GIT_DIR/refs/bisect"
+	rm -f "$GIT_DIR/refs/heads/bisect"
+	rm -f "$GIT_DIR/BISECT_LOG"
+	rm -f "$GIT_DIR/BISECT_NAMES"
+	rm -f "$GIT_DIR/BISECT_RUN"
+}
+
 bisect_replay () {
 	test -r "$1" || {
 		echo >&2 "cannot read $1 for replaying"

t/t6030-bisect-run.sh

@@ -40,8 +40,8 @@ test_expect_success \
 # We want to automatically find the commit that
 # introduced "Another" into hello.
 test_expect_success \
-    'git bisect run simple case' \
+    '"git bisect run" simple case' \
-    'echo "#!/bin/sh" > test_script.sh &&
+    'echo "#"\!"/bin/sh" > test_script.sh &&
      echo "grep Another hello > /dev/null" >> test_script.sh &&
      echo "test \$? -ne 0" >> test_script.sh &&
      chmod +x test_script.sh &&
@@ -49,7 +49,21 @@ test_expect_success \
      git bisect good $HASH1 &&
      git bisect bad $HASH4 &&
      git bisect run ./test_script.sh > my_bisect_log.txt &&
-     grep "$HASH3 is first bad commit" my_bisect_log.txt'
+     grep "$HASH3 is first bad commit" my_bisect_log.txt &&
+     git bisect reset'
+
+# We want to automatically find the commit that
+# introduced "Ciao" into hello.
+test_expect_success \
+    '"git bisect run" with more complex "git bisect start"' \
+    'echo "#"\!"/bin/sh" > test_script.sh &&
+     echo "grep Ciao hello > /dev/null" >> test_script.sh &&
+     echo "test \$? -ne 0" >> test_script.sh &&
+     chmod +x test_script.sh &&
+     git bisect start $HASH4 $HASH1 &&
+     git bisect run ./test_script.sh > my_bisect_log.txt &&
+     grep "$HASH4 is first bad commit" my_bisect_log.txt &&
+     git bisect reset'
 
 #
 #