[GSoC PATCH v5 5/5] repo: add the --format flag

[Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>]

Add the --format flag to git-repo-info. By using this flag, the users
can choose the format for obtaining the data they requested.

Given that this command can be used for generating input for other
applications and for being read by end users, it requires at least two
formats: one for being read by humans and other for being read by
machines. Some other Git commands also have two output formats, notably
git-config which was the inspiration for the two formats that were
chosen here:

- keyvalue, where the retrieved data is printed one per line, using =
  for delimiting the key and the value. This is the default format,
  targeted for end users.
- nul, where the retrieved data is separated by null characters, using
  the newline character for delimiting the key and the value. This
  format is targeted for being read by machines.

Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Justin Tobler <jltobler@gmail.com>
Mentored-by: Karthik Nayak <karthik.188@gmail.com>
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
---
 Documentation/git-repo.adoc | 13 +++++++++-
 builtin/repo.c              | 49 ++++++++++++++++++++++++++++++++++---
 t/t1900-repo.sh             | 20 +++++++++++++--
 3 files changed, 75 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-repo.adoc b/Documentation/git-repo.adoc
index 3f920b619f..6cc3ff581c 100644
--- a/Documentation/git-repo.adoc
+++ b/Documentation/git-repo.adoc
@@ -18,10 +18,21 @@ THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE.
 
 COMMANDS
 --------
-`info [<key>...]`::
+`info [--format=<format>] [<key>...]`::
 	Retrieve metadata-related information about the current repository. Only
 	the requested data will be returned based on their keys (see "INFO KEYS"
 	section below).
++
+The output format can be chosen through the flag `--format`. Two formats are
+supported:
++
+* `keyvalue`: output key-value pairs one per line using the `=` character as
+the delimiter between the key and the value. This is the default.
+
+* `nul`: similar to `keyvalue`, but using a newline character as the delimiter
+between the key and the value and using a null character after each value.
+This format is better suited for being parsed by another applications than
+`keyvalue`.
 
 INFO KEYS
 ---------
diff --git a/builtin/repo.c b/builtin/repo.c
index 37fb1803f6..a293d32b92 100644
--- a/builtin/repo.c
+++ b/builtin/repo.c
@@ -9,6 +9,11 @@
 
 typedef int get_value_fn(struct repository *repo, struct strbuf *buf);
 
+enum output_format {
+	FORMAT_KEYVALUE,
+	FORMAT_NUL_TERMINATED,
+};
+
 struct field {
 	const char *key;
 	get_value_fn *get_value;
@@ -68,9 +73,24 @@ static int qsort_strcmp(const void *va, const void *vb)
 	return strcmp(a, b);
 }
 
-static int print_fields(int argc, const char **argv, struct repository *repo)
+static int print_fields(int argc, const char **argv,
+			struct repository *repo,
+			enum output_format format)
 {
 	const char *last = "";
+	char kv_sep;
+	char field_sep;
+
+	switch (format) {
+	case FORMAT_KEYVALUE:
+		kv_sep = '=';
+		field_sep = '\n';
+		break;
+	case FORMAT_NUL_TERMINATED:
+		kv_sep = '\n';
+		field_sep = '\0';
+		break;
+	}
 
 	QSORT(argv, argc, qsort_strcmp);
 
@@ -91,7 +111,7 @@ static int print_fields(int argc, const char **argv, struct repository *repo)
 		}
 
 		get_value(repo, &value);
-		printf("%s=%s\n", key, value.buf);
+		printf("%s%c%s%c", key, kv_sep, value.buf, field_sep);
 		last = key;
 		strbuf_release(&value);
 	}
@@ -99,10 +119,31 @@ static int print_fields(int argc, const char **argv, struct repository *repo)
 	return 0;
 }
 
-static int repo_info(int argc, const char **argv, const char *prefix UNUSED,
+static int repo_info(int argc, const char **argv, const char *prefix,
 		     struct repository *repo)
 {
-	return print_fields(argc - 1, argv + 1, repo);
+	const char *format_str = "keyvalue";
+	enum output_format format;
+	const char *const repo_info_usage[] = {
+		"git repo info [<key>...]",
+		NULL
+	};
+	struct option options[] = {
+		OPT_STRING(0, "format", &format_str, N_("format"),
+			   N_("output format")),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options, repo_info_usage, 0);
+
+	if (!strcmp(format_str, "keyvalue"))
+		format = FORMAT_KEYVALUE;
+	else if (!strcmp(format_str, "nul"))
+		format = FORMAT_NUL_TERMINATED;
+	else
+		die(_("invalid format '%s'"), format_str);
+
+	return print_fields(argc, argv, repo, format);
 }
 
 int cmd_repo(int argc, const char **argv, const char *prefix,
diff --git a/t/t1900-repo.sh b/t/t1900-repo.sh
index 0bdbf6911e..94a98c52f6 100755
--- a/t/t1900-repo.sh
+++ b/t/t1900-repo.sh
@@ -20,11 +20,20 @@ test_repo_info () {
 	key=$3
 	expected_value=$4
 
-	test_expect_success "$label" '
+	test_expect_success "null-terminated: $label" '
+		test_when_finished "rm -rf repo" &&
+		eval "$init_command" &&
+		echo "$expected_value" | lf_to_nul >expected &&
+		git -C repo repo info --format=nul "$key" >output &&
+		tail -n 1 output >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "key-value: $label" '
 		test_when_finished "rm -rf repo" &&
 		eval "$init_command" &&
 		echo "$expected_value" >expected &&
-		git -C repo repo info "$key" >output &&
+		git -C repo repo info --format=keyvalue "$key" >output &&
 		cut -d "=" -f 2 <output >actual &&
 		test_cmp expected actual
 	'
@@ -81,4 +90,11 @@ test_expect_success 'output is returned correctly when two keys are requested' '
 	test_cmp expect actual
 '
 
+test_expect_success 'git-repo-info aborts when requesting an invalid format' '
+	test_when_finished "rm -f err expected" &&
+	echo "fatal: invalid format '\'foo\''" >expected &&
+	test_must_fail git repo info --format=foo 2>err &&
+	test_cmp expected err
+'
+
 test_done
-- 
2.39.5 (Apple Git-154)