[PATCH v3 5/6] help: add "-a --verbose" to list all commands with synopsis

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

This lists all recognized commands [1] by category. The group order
follows closely git.txt.

[1] We may actually show commands that are not built (e.g. if you set
NO_PERL you don't have git-instaweb but it's still listed here). I
ignore the problem because on Linux a git package could be split
anyway. The "git-core" package may not contain git-instaweb even if
it's built because it may end up in a separate package. We can't know
anyway.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-help.txt |  4 ++-
 builtin/help.c             |  7 ++++
 help.c                     | 69 ++++++++++++++++++++++++++++++++++++++
 help.h                     |  1 +
 t/t0012-help.sh            |  9 +++++
 5 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-help.txt b/Documentation/git-help.txt
index 40d328a4b3..a40fc38d8b 100644
--- a/Documentation/git-help.txt
+++ b/Documentation/git-help.txt
@@ -8,7 +8,7 @@ git-help - Display help information about Git
 SYNOPSIS
 --------
 [verse]
-'git help' [-a|--all] [-g|--guide]
+'git help' [-a|--all [--verbose]] [-g|--guide]
 	   [-i|--info|-m|--man|-w|--web] [COMMAND|GUIDE]
 
 DESCRIPTION
@@ -42,6 +42,8 @@ OPTIONS
 --all::
 	Prints all the available commands on the standard output. This
 	option overrides any given command or guide name.
+	When used with `--verbose` print description for all recognized
+	commands.
 
 -g::
 --guides::
diff --git a/builtin/help.c b/builtin/help.c
index 598867cfea..0e0af8426a 100644
--- a/builtin/help.c
+++ b/builtin/help.c
@@ -36,6 +36,7 @@ static const char *html_path;
 
 static int show_all = 0;
 static int show_guides = 0;
+static int verbose;
 static unsigned int colopts;
 static enum help_format help_format = HELP_FORMAT_NONE;
 static int exclude_guides;
@@ -48,6 +49,7 @@ static struct option builtin_help_options[] = {
 			HELP_FORMAT_WEB),
 	OPT_SET_INT('i', "info", &help_format, N_("show info page"),
 			HELP_FORMAT_INFO),
+	OPT__VERBOSE(&verbose, N_("print command description")),
 	OPT_END(),
 };
 
@@ -463,6 +465,11 @@ int cmd_help(int argc, const char **argv, const char *prefix)
 
 	if (show_all) {
 		git_config(git_help_config, NULL);
+		if (verbose) {
+			setup_pager();
+			list_all_cmds_help();
+			return 0;
+		}
 		printf(_("usage: %s%s"), _(git_usage_string), "\n\n");
 		load_command_list("git-", &main_cmds, &other_cmds);
 		list_commands(colopts, &main_cmds, &other_cmds);
diff --git a/help.c b/help.c
index 6688653f99..ae5281601a 100644
--- a/help.c
+++ b/help.c
@@ -285,6 +285,75 @@ void list_porcelain_cmds(void)
 	}
 }
 
+static int cmd_category_cmp(const void *elem1, const void *elem2)
+{
+	const struct cmdname_help *e1 = elem1;
+	const struct cmdname_help *e2 = elem2;
+
+	if (e1->category < e2->category)
+		return -1;
+	if (e1->category > e2->category)
+		return 1;
+	return strcmp(e1->name, e2->name);
+}
+
+static void list_commands_by_category(int cat, struct cmdname_help *cmds,
+				      int nr, int longest)
+{
+	int i;
+
+	for (i = 0; i < nr; i++) {
+		struct cmdname_help *cmd = cmds + i;
+
+		if (cmd->category != cat)
+			continue;
+
+		printf("   %s   ", cmd->name);
+		mput_char(' ', longest - strlen(cmd->name));
+		puts(_(cmd->help));
+	}
+}
+
+void list_all_cmds_help(void)
+{
+	int i, longest = 0;
+	int nr = ARRAY_SIZE(command_list);
+	struct cmdname_help *cmds = command_list;
+
+	for (i = 0; i < nr; i++) {
+		struct cmdname_help *cmd = cmds + i;
+
+		if (longest < strlen(cmd->name))
+			longest = strlen(cmd->name);
+	}
+
+	QSORT(cmds, nr, cmd_category_cmp);
+
+	printf("%s\n\n", _("Main Porcelain Commands"));
+	list_commands_by_category(CAT_mainporcelain, cmds, nr, longest);
+
+	printf("\n%s\n\n", _("Ancillary Commands / Manipulators"));
+	list_commands_by_category(CAT_ancillarymanipulators, cmds, nr, longest);
+
+	printf("\n%s\n\n", _("Ancillary Commands / Interrogators"));
+	list_commands_by_category(CAT_ancillaryinterrogators, cmds, nr, longest);
+
+	printf("\n%s\n\n", _("Interacting with Others"));
+	list_commands_by_category(CAT_foreignscminterface, cmds, nr, longest);
+
+	printf("\n%s\n\n", _("Low-level Commands / Manipulators"));
+	list_commands_by_category(CAT_plumbingmanipulators, cmds, nr, longest);
+
+	printf("\n%s\n\n", _("Low-level Commands / Interrogators"));
+	list_commands_by_category(CAT_plumbinginterrogators, cmds, nr, longest);
+
+	printf("\n%s\n\n", _("Low-level Commands / Synching Repositories"));
+	list_commands_by_category(CAT_synchingrepositories, cmds, nr, longest);
+
+	printf("\n%s\n\n", _("Low-level Commands / Internal Helpers"));
+	list_commands_by_category(CAT_purehelpers, cmds, nr, longest);
+}
+
 int is_in_cmdlist(struct cmdnames *c, const char *s)
 {
 	int i;
diff --git a/help.h b/help.h
index 33e2210ebd..62449f1b7e 100644
--- a/help.h
+++ b/help.h
@@ -17,6 +17,7 @@ static inline void mput_char(char c, unsigned int num)
 }
 
 extern void list_common_cmds_help(void);
+extern void list_all_cmds_help(void);
 extern void list_all_cmds(void);
 extern void list_porcelain_cmds(void);
 extern const char *help_unknown_cmd(const char *cmd);
diff --git a/t/t0012-help.sh b/t/t0012-help.sh
index fd2a7f27dc..53208ab20e 100755
--- a/t/t0012-help.sh
+++ b/t/t0012-help.sh
@@ -25,6 +25,15 @@ test_expect_success "setup" '
 	EOF
 '
 
+# make sure to exercise these code paths, the output is a bit tricky
+# to verify
+test_expect_success 'basic help commands' '
+	git help >/dev/null &&
+	git help -a >/dev/null &&
+	git help -g >/dev/null &&
+	git help -av >/dev/null
+'
+
 test_expect_success "works for commands and guides by default" '
 	configure_help &&
 	git help status &&
-- 
2.17.0.367.g5dd2e386c3