git-prompt: improve cherry-pick/revert detection

If the user commits or resets a conflict resolution in the middle of a
sequence of cherry-picks or reverts then CHERRY_PICK_HEAD/REVERT_HEAD
will be removed and so in the absence of those files we need to check
.git/sequencer/todo to see if there is a cherry-pick or revert in
progress.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-prompt.sh

@@ -286,6 +286,37 @@ __git_eread ()
 	test -r "$1" && IFS=$'\r\n' read "$2" <"$1"
 }
 
+# see if a cherry-pick or revert is in progress, if the user has committed a
+# conflict resolution with 'git commit' in the middle of a sequence of picks or
+# reverts then CHERRY_PICK_HEAD/REVERT_HEAD will not exist so we have to read
+# the todo file.
+__git_sequencer_status ()
+{
+	local todo
+	if test -f "$g/CHERRY_PICK_HEAD"
+	then
+		r="|CHERRY-PICKING"
+		return 0;
+	elif test -f "$g/REVERT_HEAD"
+	then
+		r="|REVERTING"
+		return 0;
+	elif __git_eread "$g/sequencer/todo" todo
+	then
+		case "$todo" in
+		p[\ \	]|pick[\ \	]*)
+			r="|CHERRY-PICKING"
+			return 0
+		;;
+		revert[\ \	]*)
+			r="|REVERTING"
+			return 0
+		;;
+		esac
+	fi
+	return 1
+}
+
 # __git_ps1 accepts 0 or 1 arguments (i.e., format string)
 # when called from PS1 using command substitution
 # in this mode it prints text to add to bash PS1 prompt (includes branch name)
@@ -417,10 +448,8 @@ __git_ps1 ()
 			fi
 		elif [ -f "$g/MERGE_HEAD" ]; then
 			r="|MERGING"
-		elif [ -f "$g/CHERRY_PICK_HEAD" ]; then
-			r="|CHERRY-PICKING"
-		elif [ -f "$g/REVERT_HEAD" ]; then
-			r="|REVERTING"
+		elif __git_sequencer_status; then
+			:
 		elif [ -f "$g/BISECT_LOG" ]; then
 			r="|BISECTING"
 		fi

t/t9903-bash-prompt.sh

@@ -211,8 +211,24 @@ test_expect_success 'prompt - merge' '
 
 test_expect_success 'prompt - cherry-pick' '
 	printf " (master|CHERRY-PICKING)" >expected &&
-	test_must_fail git cherry-pick b1 &&
-	test_when_finished "git reset --hard" &&
+	test_must_fail git cherry-pick b1 b1^ &&
+	test_when_finished "git cherry-pick --abort" &&
+	__git_ps1 >"$actual" &&
+	test_cmp expected "$actual" &&
+	git reset --merge &&
+	test_must_fail git rev-parse CHERRY_PICK_HEAD &&
+	__git_ps1 >"$actual" &&
+	test_cmp expected "$actual"
+'
+
+test_expect_success 'prompt - revert' '
+	printf " (master|REVERTING)" >expected &&
+	test_must_fail git revert b1^ b1 &&
+	test_when_finished "git revert --abort" &&
+	__git_ps1 >"$actual" &&
+	test_cmp expected "$actual" &&
+	git reset --merge &&
+	test_must_fail git rev-parse REVERT_HEAD &&
 	__git_ps1 >"$actual" &&
 	test_cmp expected "$actual"
 '