Merge branch 'jc/optional-path'

Configuration variables that take a pathname as a value
(e.g. blame.ignorerevsfile) can be marked as optional by prefixing
":(optoinal)" before its value.

* jc/optional-path:
  parseopt: values of pathname type can be prefixed with :(optional)
  config: values of pathname type can be prefixed with :(optional)
  t7500: fix GIT_EDITOR shell snippet
  t7500: make each piece more independent

7 files changed, 95 insertions, 25 deletions

diff --git a/Documentation/config.adoc b/Documentation/config.adoc
index 05f1ca7293..62eebe7c54 100644
--- a/Documentation/config.adoc
+++ b/Documentation/config.adoc
@@ -357,7 +357,9 @@ compiled without runtime prefix support, the compiled-in prefix will be
 substituted instead. In the unlikely event that a literal path needs to
 be specified that should _not_ be expanded, it needs to be prefixed by
 `./`, like so: `./%(prefix)/bin`.
-
++
+If prefixed with `:(optional)`, the configuration variable is treated
+as if it does not exist, if the named path does not exist.
 
 Variables
 ~~~~~~~~~
diff --git a/Documentation/gitcli.adoc b/Documentation/gitcli.adoc
index 1ea681b59d..ef2a0a399d 100644
--- a/Documentation/gitcli.adoc
+++ b/Documentation/gitcli.adoc
@@ -216,6 +216,20 @@ $ git describe --abbrev=10 HEAD  # correct
 $ git describe --abbrev 10 HEAD  # NOT WHAT YOU MEANT
 ----------------------------
 
+
+Magic filename options
+~~~~~~~~~~~~~~~~~~~~~~
+Options that take a filename allow a prefix `:(optional)`. For example:
+
+----------------------------
+git commit -F :(optional)COMMIT_EDITMSG
+# if COMMIT_EDITMSG does not exist, equivalent to
+git commit
+----------------------------
+
+Like with configuration values, if the named file is missing Git behaves as if
+the option was not given at all. See "Values" in linkgit:git-config[1].
+
 NOTES ON FREQUENTLY CONFUSED OPTIONS
 ------------------------------------
 
diff --git a/config.c b/config.c
index 74bf76a97e..71b136bf7f 100644
--- a/config.c
+++ b/config.c
@@ -1278,11 +1278,23 @@ int git_config_string(char **dest, const char *var, const char *value)
 
 int git_config_pathname(char **dest, const char *var, const char *value)
 {
+	int is_optional;
+	char *path;
+
 	if (!value)
 		return config_error_nonbool(var);
-	*dest = interpolate_path(value, 0);
-	if (!*dest)
+
+	is_optional = skip_prefix(value, ":(optional)", &value);
+	path = interpolate_path(value, 0);
+	if (!path)
 		die(_("failed to expand user dir in: '%s'"), value);
+
+	if (is_optional && is_missing_file(path)) {
+		free(path);
+		return 0;
+	}
+
+	*dest = path;
 	return 0;
 }
 
diff --git a/parse-options.c b/parse-options.c
index 992ec9631f..5933468c19 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -133,7 +133,6 @@ static enum parse_opt_result do_get_value(struct parse_opt_ctx_t *p,
 {
 	const char *arg;
 	const int unset = flags & OPT_UNSET;
-	int err;
 
 	if (unset && p->opt)
 		return error(_("%s takes no value"), optname(opt, flags));
@@ -209,21 +208,31 @@ static enum parse_opt_result do_get_value(struct parse_opt_ctx_t *p,
 	case OPTION_FILENAME:
 	{
 		const char *value;
-
-		FREE_AND_NULL(*(char **)opt->value);
-
-		err = 0;
+		int is_optional;
 
 		if (unset)
 			value = NULL;
 		else if (opt->flags & PARSE_OPT_OPTARG && !p->opt)
-			value = (const char *) opt->defval;
-		else
-			err = get_arg(p, opt, flags, &value);
+			value = (char *)opt->defval;
+		else {
+			int err = get_arg(p, opt, flags, &value);
+			if (err)
+				return err;
+		}
+		if (!value)
+			return 0;
 
-		if (!err)
-			*(char **)opt->value = fix_filename(p->prefix, value);
-		return err;
+		is_optional = skip_prefix(value, ":(optional)", &value);
+		if (!value)
+			is_optional = 0;
+		value = fix_filename(p->prefix, value);
+		if (is_optional && is_empty_or_missing_file(value)) {
+			free((char *)value);
+		} else {
+			FREE_AND_NULL(*(char **)opt->value);
+			*(const char **)opt->value = value;
+		}
+		return 0;
 	}
 	case OPTION_CALLBACK:
 	{
diff --git a/t/t7500-commit-template-squash-signoff.sh b/t/t7500-commit-template-squash-signoff.sh
index 4dca8d97a7..1935171d68 100755
--- a/t/t7500-commit-template-squash-signoff.sh
+++ b/t/t7500-commit-template-squash-signoff.sh
@@ -31,52 +31,70 @@ test_expect_success 'nonexistent template file should return error' '
 	echo changes >> foo &&
 	git add foo &&
 	(
-		GIT_EDITOR="echo hello >\"\$1\"" &&
+		GIT_EDITOR="echo hello >" &&
 		export GIT_EDITOR &&
 		test_must_fail git commit --template "$PWD"/notexist
 	)
 '
 
+test_expect_success 'nonexistent optional template file on command line' '
+	echo changes >> foo &&
+	git add foo &&
+	(
+		GIT_EDITOR="echo hello >\"\$1\"" &&
+		export GIT_EDITOR &&
+		git commit --template ":(optional)$PWD/notexist"
+	)
+'
+
 test_expect_success 'nonexistent template file in config should return error' '
 	test_config commit.template "$PWD"/notexist &&
 	(
-		GIT_EDITOR="echo hello >\"\$1\"" &&
+		GIT_EDITOR="echo hello >" &&
 		export GIT_EDITOR &&
-		test_must_fail git commit
+		test_must_fail git commit --allow-empty
 	)
 '
 
+test_expect_success 'nonexistent optional template file in config' '
+	test_config commit.template ":(optional)$PWD"/notexist &&
+	GIT_EDITOR="echo hello >" git commit --allow-empty &&
+	git cat-file commit HEAD | sed -e "1,/^$/d" >actual &&
+	echo hello >expect &&
+	test_cmp expect actual
+'
+
 # From now on we'll use a template file that exists.
 TEMPLATE="$PWD"/template
 
 test_expect_success 'unedited template should not commit' '
-	echo "template line" > "$TEMPLATE" &&
-	test_must_fail git commit --template "$TEMPLATE"
+	echo "template line" >"$TEMPLATE" &&
+	test_must_fail git commit --allow-empty --template "$TEMPLATE"
 '
 
 test_expect_success 'unedited template with comments should not commit' '
-	echo "# comment in template" >> "$TEMPLATE" &&
-	test_must_fail git commit --template "$TEMPLATE"
+	echo "# comment in template" >>"$TEMPLATE" &&
+	test_must_fail git commit --allow-empty --template "$TEMPLATE"
 '
 
 test_expect_success 'a Signed-off-by line by itself should not commit' '
 	(
 		test_set_editor "$TEST_DIRECTORY"/t7500/add-signed-off &&
-		test_must_fail git commit --template "$TEMPLATE"
+		test_must_fail git commit --allow-empty --template "$TEMPLATE"
 	)
 '
 
 test_expect_success 'adding comments to a template should not commit' '
 	(
 		test_set_editor "$TEST_DIRECTORY"/t7500/add-comments &&
-		test_must_fail git commit --template "$TEMPLATE"
+		test_must_fail git commit --allow-empty --template "$TEMPLATE"
 	)
 '
 
 test_expect_success 'adding real content to a template should commit' '
 	(
 		test_set_editor "$TEST_DIRECTORY"/t7500/add-content &&
-		git commit --template "$TEMPLATE"
+		git commit --allow-empty --template "$TEMPLATE"
 	) &&
 	commit_msg_is "template linecommit message"
 '
diff --git a/wrapper.c b/wrapper.c
index 2f00d2ac87..3d507d4204 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -721,6 +721,19 @@ int xgethostname(char *buf, size_t len)
 	return ret;
 }
 
+int is_missing_file(const char *filename)
+{
+	struct stat st;
+
+	if (stat(filename, &st) < 0) {
+		if (errno == ENOENT)
+			return 1;
+		die_errno(_("could not stat %s"), filename);
+	}
+
+	return 0;
+}
+
 int is_empty_or_missing_file(const char *filename)
 {
 	struct stat st;
diff --git a/wrapper.h b/wrapper.h
index 7df824e34a..44a8597ac3 100644
--- a/wrapper.h
+++ b/wrapper.h
@@ -66,7 +66,9 @@ void write_file_buf(const char *path, const char *buf, size_t len);
 __attribute__((format (printf, 2, 3)))
 void write_file(const char *path, const char *fmt, ...);
 
-/* Return 1 if the file is empty or does not exists, 0 otherwise. */
+/* Return 1 if the file does not exist, 0 otherwise. */
+int is_missing_file(const char *filename);
+/* Return 1 if the file is empty or does not exist, 0 otherwise. */
 int is_empty_or_missing_file(const char *filename);
 
 enum fsync_action {