[PATCH v2] pathspec: advice: long and short forms are incompatible

[Stavros Ntentos <stdedos@gmail.com>]

It can be a "reasonable" mistake to mix short and long forms,
e.g. `:!(glob)`, instead of the (correct) `:(exclude,glob)`.

Teach git to issue an advice when such a pathspec is given.
	i.e.: While in short form parsing:
	* if the string contains an open parenthesis [`(`], and
	* without having explicitly terminated magic parsing (`:`)
	issue an advice hinting to that fact.

Based on "Junio C Hamano <gitster@pobox.com>"'s code suggestion
(in https://lore.kernel.org/git/xmqqa6qoqw9n.fsf@gitster.g/).

Signed-off-by: Stavros Ntentos <133706+stdedos@users.noreply.github.com>
---
 Documentation/config/advice.txt |  5 +++++
 advice.c                        |  3 +++
 advice.h                        |  2 ++
 pathspec.c                      | 16 ++++++++++++++
 t/t6132-pathspec-exclude.sh     | 37 +++++++++++++++++++++++++++++++++
 5 files changed, 63 insertions(+)

diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index acbd0c09aa..f7ccd05c3a 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -119,4 +119,9 @@ advice.*::
 	addEmptyPathspec::
 		Advice shown if a user runs the add command without providing
 		the pathspec parameter.
+	mixedShortLongMagic::
+		Advice shown if a user provides a pathspec that could be
+		interpreted as a mixed short and long magic modifier(s)
+		(i.e. contains an open parenthesis `(` without explictly
+		terminating pathspec magic parsing with `:`).
 --
diff --git a/advice.c b/advice.c
index 164742305f..6630c57678 100644
--- a/advice.c
+++ b/advice.c
@@ -33,6 +33,7 @@ int advice_checkout_ambiguous_remote_branch_name = 1;
 int advice_submodule_alternate_error_strategy_die = 1;
 int advice_add_ignored_file = 1;
 int advice_add_empty_pathspec = 1;
+int advice_mixed_short_long_magic_pathspec = 1;
 
 static int advice_use_color = -1;
 static char advice_colors[][COLOR_MAXLEN] = {
@@ -95,6 +96,7 @@ static struct {
 	{ "submoduleAlternateErrorStrategyDie", &advice_submodule_alternate_error_strategy_die },
 	{ "addIgnoredFile", &advice_add_ignored_file },
 	{ "addEmptyPathspec", &advice_add_empty_pathspec },
+	{ "mixedShortLongMagicPathspec", &advice_mixed_short_long_magic_pathspec },
 
 	/* make this an alias for backward compatibility */
 	{ "pushNonFastForward", &advice_push_update_rejected }
@@ -137,6 +139,7 @@ static struct {
 	[ADVICE_STATUS_U_OPTION]			= { "statusUoption", 1 },
 	[ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE] = { "submoduleAlternateErrorStrategyDie", 1 },
 	[ADVICE_WAITING_FOR_EDITOR]			= { "waitingForEditor", 1 },
+	[ADVICE_MIXED_SHORT_LONG_MAGIC_PATHSPEC]	= { "mixedShortLongMagicPathspec", 1 },
 };
 
 static const char turn_off_instructions[] =
diff --git a/advice.h b/advice.h
index bc2432980a..050f058274 100644
--- a/advice.h
+++ b/advice.h
@@ -33,6 +33,7 @@ extern int advice_checkout_ambiguous_remote_branch_name;
 extern int advice_submodule_alternate_error_strategy_die;
 extern int advice_add_ignored_file;
 extern int advice_add_empty_pathspec;
+extern int advice_mixed_short_long_magic_pathspec;
 
 /*
  * To add a new advice, you need to:
@@ -72,6 +73,7 @@ extern int advice_add_empty_pathspec;
 	ADVICE_STATUS_U_OPTION,
 	ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE,
 	ADVICE_WAITING_FOR_EDITOR,
+	ADVICE_MIXED_SHORT_LONG_MAGIC_PATHSPEC,
 };
 
 int git_default_advice_config(const char *var, const char *value);
diff --git a/pathspec.c b/pathspec.c
index 18b3be362a..085a624ad9 100644
--- a/pathspec.c
+++ b/pathspec.c
@@ -336,6 +336,11 @@ static const char *parse_long_magic(unsigned *magic, int *prefix_len,
 	return pos;
 }
 
+static const char mixed_pathspec_magic[] = N_(
+	"'%.*s...': cannot mix shortform magic with longform [e.g. like :(glob)].\n"
+	"If '%.*s...' is a valid path, explicitly terminate magic parsing with ':'; or");
+static int extra_lookahead_chars = 7;
+
 /*
  * Parse the pathspec element looking for short magic
  *
@@ -356,6 +361,17 @@ static const char *parse_short_magic(unsigned *magic, const char *elem)
 			continue;
 		}
 
+		if (ch == '(') {
+			/*
+			 * a possible mistake: once you started a shortform
+			 * you cannot add a longform, e.g. ":!(top)"
+			 */
+			advise_if_enabled(ADVICE_MIXED_SHORT_LONG_MAGIC_PATHSPEC,
+			                  _(mixed_pathspec_magic),
+			                  (int)(pos-elem+extra_lookahead_chars), elem,
+			                  extra_lookahead_chars, pos);
+		}
+
 		if (!is_pathspec_magic(ch))
 			break;
 
diff --git a/t/t6132-pathspec-exclude.sh b/t/t6132-pathspec-exclude.sh
index 30328b87f0..b5d51c1429 100755
--- a/t/t6132-pathspec-exclude.sh
+++ b/t/t6132-pathspec-exclude.sh
@@ -244,4 +244,41 @@ test_expect_success 'grep --untracked PATTERN :(exclude)*FILE' '
 	test_cmp expect-grep actual-grep
 '
 
+cat > expected_warn <<"EOF"
+hint: ':!(glob)*...': cannot mix shortform magic with longform [e.g. like :(glob)].
+hint: If '(glob)*...' is a valid path, explicitly terminate magic parsing with ':'; or
+hint: Disable this message with "git config advice.mixedShortLongMagicPathspec false"
+EOF
+test_expect_success 'warn pathspec not matching longform magic in :!(...)' '
+	git log --oneline --format=%s -- '"'"':!(glob)**/file'"'"' >actual 2>warn &&
+	cat <<EOF >expect &&
+sub2/file
+sub/sub/sub/file
+sub/file2
+sub/sub/file
+sub/file
+file
+EOF
+	cat actual &&
+	cat warn &&
+	test_cmp expect actual &&
+	test_cmp expected_warn warn
+'
+
+test_expect_success 'do not warn pathspec not matching longform magic in :!:(...) (i.e. if magic parsing is explicitly stopped)' '
+	git log --oneline --format=%s -- '"'"':!:(glob)**/file'"'"' >actual 2>warn &&
+	cat <<EOF >expect &&
+sub2/file
+sub/sub/sub/file
+sub/file2
+sub/sub/file
+sub/file
+file
+EOF
+	cat actual &&
+	cat warn &&
+	test_cmp expect actual &&
+	! test_cmp expected_warn warn
+'
+
 test_done
-- 
2.31.0