bisect: move argument parsing before state modification.

Currently 'git bisect start' modifies some state prior to checking
that its arguments are valid.

This change moves argument validation before state modification
with the effect that state modification does not occur
unless argument validations succeeds.

An existing test is changed to check that new bisect state
is not created if arguments are invalid.

A new test is added to check that existing bisect state
is not modified if arguments are invalid.

Signed-off-by: Jon Seymour <jon.seymour@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 33 insertions, 33 deletions

diff --git a/git-bisect.sh b/git-bisect.sh
index b2186a862..20f6dd562 100755
--- a/git-bisect.sh
+++ b/git-bisect.sh
@@ -60,6 +60,39 @@ bisect_autostart() {
 
 bisect_start() {
 	#
+	# Check for one bad and then some good revisions.
+	#
+	has_double_dash=0
+	for arg; do
+	    case "$arg" in --) has_double_dash=1; break ;; esac
+	done
+	orig_args=$(git rev-parse --sq-quote "$@")
+	bad_seen=0
+	eval=''
+	while [ $# -gt 0 ]; do
+	    arg="$1"
+	    case "$arg" in
+	    --)
+		shift
+		break
+		;;
+	    *)
+		rev=$(git rev-parse -q --verify "$arg^{commit}") || {
+		    test $has_double_dash -eq 1 &&
+			die "$(eval_gettext "'\$arg' does not appear to be a valid revision")"
+		    break
+		}
+		case $bad_seen in
+		0) state='bad' ; bad_seen=1 ;;
+		*) state='good' ;;
+		esac
+		eval="$eval bisect_write '$state' '$rev' 'nolog'; "
+		shift
+		;;
+	    esac
+	done
+
+	#
 	# Verify HEAD.
 	#
 	head=$(GIT_DIR="$GIT_DIR" git symbolic-ref -q HEAD) ||
@@ -98,39 +131,6 @@ bisect_start() {
 	bisect_clean_state || exit
 
 	#
-	# Check for one bad and then some good revisions.
-	#
-	has_double_dash=0
-	for arg; do
-	    case "$arg" in --) has_double_dash=1; break ;; esac
-	done
-	orig_args=$(git rev-parse --sq-quote "$@")
-	bad_seen=0
-	eval=''
-	while [ $# -gt 0 ]; do
-	    arg="$1"
-	    case "$arg" in
-	    --)
-		shift
-		break
-		;;
-	    *)
-		rev=$(git rev-parse -q --verify "$arg^{commit}") || {
-		    test $has_double_dash -eq 1 &&
-			die "$(eval_gettext "'\$arg' does not appear to be a valid revision")"
-		    break
-		}
-		case $bad_seen in
-		0) state='bad' ; bad_seen=1 ;;
-		*) state='good' ;;
-		esac
-		eval="$eval bisect_write '$state' '$rev' 'nolog'; "
-		shift
-		;;
-	    esac
-	done
-
-	#
 	# Change state.
 	# In case of mistaken revs or checkout error, or signals received,
 	# "bisect_auto_next" below may exit or misbehave.