[PATCH 08/15] for-each-ref: get --pretty using format_commit_message

[Ramkumar Ramachandra <artagnon@gmail.com>]

From: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>

--format is very limited in its capabilities.  Introduce --pretty, which
extends the existing --format with pretty-formats.  In --pretty:

 - Existing --format %(atom) is available. They also accept some pretty
   magic.  For example, you can use "% (atom)" to only display a leading
   space if the atom produces something.

 - %ab to display a hex character 0xab is not available as it may
   conflict with other pretty's placeholders.  Use %xab instead.

 - Many pretty placeholders are designed to work on commits.  While some
   of them should work on tags too, they don't (yet).

 - Unsupported atoms cause for-each-ref to exit early and report.
   Unsupported pretty placeholders are displayed as-is.

 - Pretty placeholders can not be used as a sorting criteria.

--format is considered deprecated. If the user hits a bug specific in
--format code, they are advised to migrate to --pretty.

[rr: documentation]

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 Documentation/git-for-each-ref.txt | 22 ++++++++++++-
 builtin/for-each-ref.c             | 67 ++++++++++++++++++++++++++++++++++++--
 2 files changed, 85 insertions(+), 4 deletions(-)

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index f2e08d1..6135812 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -9,7 +9,8 @@ SYNOPSIS
 --------
 [verse]
 'git for-each-ref' [--count=<count>] [--shell|--perl|--python|--tcl]
-		   [(--sort=<key>)...] [--format=<format>] [<pattern>...]
+		   [(--sort=<key>)...] [--format=<format>|--pretty=<pretty>]
+		   [<pattern>...]
 
 DESCRIPTION
 -----------
@@ -47,6 +48,25 @@ OPTIONS
 	`xx`; for example `%00` interpolates to `\0` (NUL),
 	`%09` to `\t` (TAB) and `%0a` to `\n` (LF).
 
+<pretty>::
+	A format string with supporting placeholders described in the
+	"PRETTY FORMATS" section in linkgit:git-log[1].  Additionally
+	supports placeholders from `<format>`
+	(i.e. `%[*](fieldname)`).
++
+Caveats:
+
+1. Many of the placeholders in "PRETTY FORMATS" are designed to work
+   specifically on commit objects: when non-commit objects are
+   supplied, those placeholders won't work.
+
+2. Does not interpolate `%ab` (where `ab` are hex digits) with the
+   corresponding hex code.  To print a byte from a hex code, use
+   `%xab` (from pretty-formats) instead.
+
+3. Only the placeholders inherited from `<format>` will respect
+   quoting settings.
+
 <pattern>...::
 	If one or more patterns are given, only refs are shown that
 	match against at least one pattern, either using fnmatch(3) or
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index e2d6c5a..576a882 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -962,6 +962,58 @@ static void show_refs(struct refinfo **refs, int maxcount,
 	strbuf_release(&sb);
 }
 
+struct format_one_atom_context {
+	struct refinfo *info;
+	int quote_style;
+};
+
+static size_t format_one_atom(struct strbuf *sb, const char *placeholder,
+			      void *format_context, void *user_data,
+			      struct strbuf *subst)
+{
+	struct format_one_atom_context *ctx = user_data;
+	const char *ep;
+
+	if (*placeholder == '%') {
+		strbuf_addch(sb, '%');
+		return 1;
+	}
+
+	if (*placeholder != '(')
+		return 0;
+
+	ep = strchr(placeholder + 1, ')');
+	if (!ep)
+		return 0;
+	print_value(sb, ctx->info, parse_atom(placeholder + 1, ep),
+		    ctx->quote_style);
+	return ep + 1 - placeholder;
+}
+
+static void show_pretty_refs(struct refinfo **refs, int maxcount,
+			     const char *format, int quote_style)
+{
+	struct pretty_print_context ctx = {0};
+	struct format_one_atom_context fctx;
+	struct strbuf sb = STRBUF_INIT;
+	int i;
+
+	ctx.format = format_one_atom;
+	ctx.user_data = &fctx;
+	fctx.quote_style = quote_style;
+	for (i = 0; i < maxcount; i++) {
+		struct commit *commit = NULL;
+		fctx.info = refs[i];
+		if (sha1_object_info(refs[i]->objectname, NULL) == OBJ_COMMIT)
+			commit = lookup_commit(refs[i]->objectname);
+		strbuf_reset(&sb);
+		format_commit_message(commit, format, &sb, &ctx);
+		strbuf_addch(&sb, '\n');
+		fputs(sb.buf, stdout);
+	}
+	strbuf_release(&sb);
+}
+
 static struct ref_sort *default_sort(void)
 {
 	static const char cstr_name[] = "refname";
@@ -1003,7 +1055,9 @@ static char const * const for_each_ref_usage[] = {
 int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 {
 	int num_refs;
-	const char *format = "%(objectname) %(objecttype)\t%(refname)";
+	const char *default_format = "%(objectname) %(objecttype)\t%(refname)";
+	const char *format = default_format;
+	const char *pretty = NULL;
 	struct ref_sort *sort = NULL, **sort_tail = &sort;
 	int maxcount = 0, quote_style = 0;
 	struct refinfo **refs;
@@ -1022,6 +1076,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 		OPT_GROUP(""),
 		OPT_INTEGER( 0 , "count", &maxcount, N_("show only <n> matched refs")),
 		OPT_STRING(  0 , "format", &format, N_("format"), N_("format to use for the output")),
+		OPT_STRING(  0 , "pretty", &pretty, N_("format"), N_("alternative format to use for the output")),
 		OPT_CALLBACK(0 , "sort", sort_tail, N_("key"),
 			    N_("field name to sort on"), &opt_parse_sort),
 		OPT_END(),
@@ -1036,7 +1091,10 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 		error("more than one quoting style?");
 		usage_with_options(for_each_ref_usage, opts);
 	}
-	if (verify_format(format))
+	if (format != default_format && pretty)
+		die("--format and --pretty cannot be used together");
+	if ((pretty && verify_format(pretty)) ||
+	    (!pretty && verify_format(format)))
 		usage_with_options(for_each_ref_usage, opts);
 
 	if (!sort)
@@ -1057,6 +1115,9 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	if (!maxcount || num_refs < maxcount)
 		maxcount = num_refs;
 
-	show_refs(refs, maxcount, format, quote_style);
+	if (pretty)
+		show_pretty_refs(refs, maxcount, pretty, quote_style);
+	else
+		show_refs(refs, maxcount, format, quote_style);
 	return 0;
 }
-- 
1.8.3.GIT