git-bisect: allow bisecting with only one bad commit.

This allows you to say:

	git bisect start
	git bisect bad $bad
	git bisect next

to start bisection without knowing a good commit.  This would
have you try a commit that is half-way since the beginning of
the history, which is rather wasteful if you already know a good
commit, but if you don't (or your history is short enough that
you do not care), there is no reason not to allow this.

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

diff --git a/git-bisect.sh b/git-bisect.sh
index c936533883a20f6d4f9879f56c750e4b37383a92..85c374e21e7076cae8f186afe899437bda1ac770 100755 (executable)
--- a/git-bisect.sh
+++ b/git-bisect.sh
@@ -168,26 +168,40 @@ bisect_write_good() {
 }
 
 bisect_next_check() {
-       next_ok=no
-       git show-ref -q --verify refs/bisect/bad &&
-       test -n "$(git for-each-ref "refs/bisect/good-*")" &&
-       next_ok=yes
-
-       case "$next_ok,$1" in
-       no,) false ;;
-       no,fail)
-           THEN=''
-           test -d "$GIT_DIR/refs/bisect" || {
-               echo >&2 'You need to start by "git bisect start".'
-               THEN='then '
-           }
-           echo >&2 'You '$THEN'need to give me at least one good' \
-               'and one bad revisions.'
-           echo >&2 '(You can use "git bisect bad" and' \
-               '"git bisect good" for that.)'
-           exit 1 ;;
+       missing_good= missing_bad=
+       git show-ref -q --verify refs/bisect/bad || missing_bad=t
+       test -n "$(git for-each-ref "refs/bisect/good-*")" || missing_good=t
+
+       case "$missing_good,$missing_bad,$1" in
+       ,,*)
+               : have both good and bad - ok
+               ;;
+       *,)
+               # do not have both but not asked to fail - just report.
+               false
+               ;;
+       t,,good)
+               # have bad but not good.  we could bisect although
+               # this is less optimum.
+               echo >&2 'Warning: bisecting only with a bad commit.'
+               if test -t 0
+               then
+                       printf >&2 'Are you sure [Y/n]? '
+                       case "$(read yesno)" in [Nn]*) exit 1 ;; esac
+               fi
+               : bisect without good...
+               ;;
        *)
-           true ;;
+               THEN=''
+               test -d "$GIT_DIR/refs/bisect" || {
+                       echo >&2 'You need to start by "git bisect start".'
+                       THEN='then '
+               }
+               echo >&2 'You '$THEN'need to give me at least one good' \
+                       'and one bad revisions.'
+               echo >&2 '(You can use "git bisect bad" and' \
+                       '"git bisect good" for that.)'
+               exit 1 ;;
        esac
 }
 
@@ -198,27 +212,32 @@ bisect_auto_next() {
 bisect_next() {
         case "$#" in 0) ;; *) usage ;; esac
        bisect_autostart
-       bisect_next_check fail
+       bisect_next_check good
+
        bad=$(git-rev-parse --verify refs/bisect/bad) &&
-       good=$(git-rev-parse --sq --revs-only --not \
-               $(cd "$GIT_DIR" && ls refs/bisect/good-*)) &&
-       rev=$(eval "git-rev-list --bisect $good $bad -- $(cat "$GIT_DIR/BISECT_NAMES")") || exit
-       if [ -z "$rev" ]; then
-           echo "$bad was both good and bad"
-           exit 1
+       good=$(git for-each-ref --format='^%(objectname)' \
+               "refs/bisect/good-*" | tr '[\012]' ' ') &&
+       eval="git-rev-list --bisect-vars $good $bad --" &&
+       eval="$eval $(cat "$GIT_DIR/BISECT_NAMES")" &&
+       eval=$(eval "$eval") &&
+       eval "$eval" || exit
+
+       if [ -z "$bisect_rev" ]; then
+               echo "$bad was both good and bad"
+               exit 1
        fi
-       if [ "$rev" = "$bad" ]; then
-           echo "$rev is first bad commit"
-           git-diff-tree --pretty $rev
-           exit 0
+       if [ "$bisect_rev" = "$bad" ]; then
+               echo "$bisect_rev is first bad commit"
+               git-diff-tree --pretty $bisect_rev
+               exit 0
        fi
-       nr=$(eval "git-rev-list $rev $good -- $(cat $GIT_DIR/BISECT_NAMES)" | wc -l) || exit
-       echo "Bisecting: $nr revisions left to test after this"
-       echo "$rev" > "$GIT_DIR/refs/heads/new-bisect"
+
+       echo "Bisecting: $bisect_nr revisions left to test after this"
+       echo "$bisect_rev" >"$GIT_DIR/refs/heads/new-bisect"
        git checkout -q new-bisect || exit
        mv "$GIT_DIR/refs/heads/new-bisect" "$GIT_DIR/refs/heads/bisect" &&
        GIT_DIR="$GIT_DIR" git-symbolic-ref HEAD refs/heads/bisect
-       git-show-branch "$rev"
+       git-show-branch "$bisect_rev"
 }
 
 bisect_visualize() {

diff --git a/t/t6030-bisect-run.sh b/t/t6030-bisect-run.sh
index 4910ff68416c8d59da6851459debeb198987b7c7..de3123522aba7d4a371cc30d8fbbd74f4d063d19 100755 (executable)
--- a/t/t6030-bisect-run.sh
+++ b/t/t6030-bisect-run.sh
@@ -4,6 +4,8 @@
 #
 test_description='Tests git-bisect functionality'
 
+exec </dev/null
+
 . ./test-lib.sh
 
 add_line_into_file()
@@ -37,21 +39,14 @@ test_expect_success \
      HASH3=$(git rev-list HEAD | head -2 | tail -1) &&
      HASH4=$(git rev-list HEAD | head -1)'
 
-test_expect_success 'bisect does not start with only one bad' '
+test_expect_success 'bisect starts with only one bad' '
        git bisect reset &&
        git bisect start &&
-       git bisect bad $HASH4 || return 1
-
-       if git bisect next
-       then
-               echo Oops, should have failed.
-               false
-       else
-               :
-       fi
+       git bisect bad $HASH4 &&
+       git bisect next
 '
 
-test_expect_success 'bisect does not start with only one good' '
+test_expect_success 'bisect starts with only one good' '
        git bisect reset &&
        git bisect start &&
        git bisect good $HASH1 || return 1