[RFC/PATCH 3/9] ref-filter: support printing N lines from tag annotation

[Karthik Nayak <karthik.188@gmail.com>]

In 'tag.c' we can print N lines from the annotation of the tag
using the '-n<num>' option. Copy code from 'tag.c' to 'ref-filter'
and modify 'ref-filter' to support printing of N lines from the
annotation of tags.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
---
 builtin/for-each-ref.c |  2 +-
 builtin/tag.c          |  4 ++++
 ref-filter.c           | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
 ref-filter.h           |  3 ++-
 4 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 5868c48..c318e33 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -74,7 +74,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	if (!maxcount || array.nr < maxcount)
 		maxcount = array.nr;
 	for (i = 0; i < maxcount; i++)
-		show_ref_array_item(array.items[i], format, quote_style);
+		show_ref_array_item(array.items[i], format, quote_style, 0);
 	ref_array_clear(&array);
 	return 0;
 }
diff --git a/builtin/tag.c b/builtin/tag.c
index 767162e..9f300e0 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -180,6 +180,10 @@ static enum contains_result contains(struct commit *candidate,
 	return contains_test(candidate, want);
 }
 
+/*
+ * Currently dupplicated in ref-filter, will eventually be removed as
+ * we port tag.c to use ref-filter APIs.
+ */
 static void show_tag_lines(const struct object_id *oid, int lines)
 {
 	int i;
diff --git a/ref-filter.c b/ref-filter.c
index 97432d1..57a5cfb 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -1262,7 +1262,48 @@ static void emit(const char *cp, const char *ep)
 	}
 }
 
-void show_ref_array_item(struct ref_array_item *info, const char *format, int quote_style)
+/* Print 'lines' no of lines of a given oid */
+static void show_tag_lines(const struct object_id *oid, int lines)
+{
+	int i;
+	unsigned long size;
+	enum object_type type;
+	char *buf, *sp, *eol;
+	size_t len;
+
+	buf = read_sha1_file(oid->hash, &type, &size);
+	if (!buf)
+		die_errno("unable to read object %s", oid_to_hex(oid));
+	if (type != OBJ_COMMIT && type != OBJ_TAG)
+		goto free_return;
+	if (!size)
+		die("an empty %s object %s?",
+		    typename(type), oid_to_hex(oid));
+
+	/* skip header */
+	sp = strstr(buf, "\n\n");
+	if (!sp)
+		goto free_return;
+
+	/* only take up to "lines" lines, and strip the signature from a tag */
+	if (type == OBJ_TAG)
+		size = parse_signature(buf, size);
+	for (i = 0, sp += 2; i < lines && sp < buf + size; i++) {
+		if (i)
+			printf("\n    ");
+		eol = memchr(sp, '\n', size - (sp - buf));
+		len = eol ? eol - sp : size - (sp - buf);
+		fwrite(sp, len, 1, stdout);
+		if (!eol)
+			break;
+		sp = eol + 1;
+	}
+free_return:
+	free(buf);
+}
+
+void show_ref_array_item(struct ref_array_item *info, const char *format,
+			 int quote_style, unsigned int lines)
 {
 	const char *cp, *sp, *ep;
 
@@ -1288,6 +1329,11 @@ void show_ref_array_item(struct ref_array_item *info, const char *format, int qu
 		resetv.s = color;
 		print_value(&resetv, quote_style);
 	}
+	if (lines > 0) {
+		struct object_id oid;
+		hashcpy(oid.hash, info->objectname);
+		show_tag_lines(&oid, lines);
+	}
 	putchar('\n');
 }
 
diff --git a/ref-filter.h b/ref-filter.h
index dd28d17..6b6fb96 100644
--- a/ref-filter.h
+++ b/ref-filter.h
@@ -55,6 +55,7 @@ struct ref_filter {
 	struct commit *merge_commit;
 
 	unsigned int with_commit_tag_algo: 1;
+	unsigned int lines;
 };
 
 struct ref_filter_cbdata {
@@ -87,7 +88,7 @@ int verify_ref_format(const char *format);
 /*  Sort the given ref_array as per the ref_sorting provided */
 void ref_array_sort(struct ref_sorting *sort, struct ref_array *array);
 /*  Print the ref using the given format and quote_style */
-void show_ref_array_item(struct ref_array_item *info, const char *format, int quote_style);
+void show_ref_array_item(struct ref_array_item *info, const char *format, int quote_style, unsigned int lines);
 /*  Callback function for parsing the sort option */
 int parse_opt_ref_sorting(const struct option *opt, const char *arg, int unset);
 /*  Default sort option based on refname */
-- 
2.4.4