Keep bisection log so that it can be replayed later.

The 'git bisect' command was very unforgiving in that once you made a
mistake telling it good/bad it was very hard to take it back.  Keep a
log of what you told it in an earlier session, so that it can be
replayed after removing everything after what you botched last time.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/git-bisect.sh b/git-bisect.sh
index 605d58a..a5be3a7 100755 (executable)
--- a/git-bisect.sh
+++ b/git-bisect.sh
@@ -8,7 +8,9 @@ git bisect bad [<rev>]          mark <rev> a known-bad revision.
 git bisect good [<rev>...]     mark <rev>... known-good revisions.
 git bisect next                        find next bisection to test and check it out.
 git bisect reset [<branch>]    finish bisection search and go back to branch.
-git bisect visualize            show bisect status in gitk.'
+git bisect visualize            show bisect status in gitk.
+git bisect replay <logfile>    replay bisection log
+git bisect log                 show bisect log.'
     exit 1
 }
 
@@ -54,6 +56,7 @@ bisect_start() {
        rm -f "$GIT_DIR/refs/heads/bisect"
        rm -rf "$GIT_DIR/refs/bisect/"
        mkdir "$GIT_DIR/refs/bisect"
+       echo "git-bisect start" >"$GIT_DIR/BISECT_LOG"
 }
 
 bisect_bad() {
@@ -66,7 +69,9 @@ bisect_bad() {
        *)
                usage ;;
        esac || exit
-       echo "$rev" > "$GIT_DIR/refs/bisect/bad"
+       echo "$rev" >"$GIT_DIR/refs/bisect/bad"
+       echo "# bad: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
+       echo "git-bisect bad $rev" >>"$GIT_DIR/BISECT_LOG"
        bisect_auto_next
 }
 
@@ -81,6 +86,8 @@ bisect_good() {
        do
                rev=$(git-rev-parse --verify "$rev") || exit
                echo "$rev" >"$GIT_DIR/refs/bisect/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
 }
@@ -129,6 +136,7 @@ bisect_next() {
        git checkout new-bisect || exit
        mv "$GIT_DIR/refs/heads/new-bisect" "$GIT_DIR/refs/heads/bisect" &&
        ln -sf refs/heads/bisect "$GIT_DIR/HEAD"
+       git-show-branch "$rev"
 }
 
 bisect_visualize() {
@@ -149,7 +157,39 @@ bisect_reset() {
        esac
        git checkout "$branch" &&
        rm -fr "$GIT_DIR/refs/bisect"
-       rm -f "$GIT_DIR/refs/reads/bisect"
+       rm -f "$GIT_DIR/refs/heads/bisect"
+       rm -f "$GIT_DIR/BISECT_LOG"
+}
+
+bisect_replay () {
+       test -r "$1" || {
+               echo >&2 "cannot read $1 for replaying"
+               exit 1
+       }
+       bisect_reset
+       while read bisect command rev
+       do
+               test "$bisect" = "git-bisect" || continue
+               case "$command" in
+               start)
+                       bisect_start
+                       ;;
+               good)
+                       echo "$rev" >"$GIT_DIR/refs/bisect/good-$rev"
+                       echo "# good: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
+                       echo "git-bisect good $rev" >>"$GIT_DIR/BISECT_LOG"
+                       ;;
+               bad)
+                       echo "$rev" >"$GIT_DIR/refs/bisect/bad"
+                       echo "# bad: "$(git-show-branch $rev) >>"$GIT_DIR/BISECT_LOG"
+                       echo "git-bisect bad $rev" >>"$GIT_DIR/BISECT_LOG"
+                       ;;
+               *)
+                       echo >&2 "?? what are you talking about?"
+                       exit 1 ;;
+               esac
+       done <"$1"
+       bisect_auto_next
 }
 
 case "$#" in
@@ -172,6 +212,10 @@ case "$#" in
        bisect_visualize "$@" ;;
     reset)
         bisect_reset "$@" ;;
+    replay)
+       bisect_replay "$@" ;;
+    log)
+       cat "$GIT_DIR/BISECT_LOG" ;;
     *)
         usage ;;
     esac