Re: [PATCH v14 07/13] ref-filter: add support for %(contents:lines=X)

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 it to support appending of N lines from the annotation of tags
to the given strbuf.

Implement %(contents:lines=X) where X lines of the given object are
obtained.

Add documentation and test for the same.

Signed-off-by: Karthik Nayak <redacted>
---

diff --git a/builtin/tag.c b/builtin/tag.c
index 471d6b1..0fc7557 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c

@@ -63,6 +64,11 @@ struct align {
        unsigned int width;
 };

+struct contents {
+       unsigned int lines;
+       struct object_id oid;
+};
+
 #define REF_FORMATTING_STATE_INIT  { 0, NULL }

 struct ref_formatting_stack {

@@ -80,6 +86,7 @@ struct ref_formatting_state {
 struct atom_value {
        const char *s;
        struct align *align;
+       struct contents *contents;

        void (*handler)(struct atom_value *atomv, struct ref_formatting_state *state);
        unsigned long ul; /* used for sorting when not FIELD_STR */
 };

@@ -569,6 +576,61 @@ static void find_subpos(const char *buf, unsigned long sz,
        *nonsiglen = *sig - buf;
 }

+/*
+ * If 'lines' is greater than 0, append that many lines from the given
+ * object_id 'oid' to the given strbuf.
+ */
+static void append_tag_lines(struct strbuf *out, 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)
+                       strbuf_addstr(out, "\n    ");
+               eol = memchr(sp, '\n', size - (sp - buf));
+               len = eol ? eol - sp : size - (sp - buf);
+               strbuf_add(out, sp, len);
+               if (!eol)
+                       break;
+               sp = eol + 1;
+       }
+free_return:
+       free(buf);
+}

+       struct strbuf s = STRBUF_INIT;
+
+       append_tag_lines(&s, &contents->oid, contents->lines);
+       quote_formatting(&state->stack->output, s.buf, state->quote_style);
+       strbuf_release(&s);
+
+       free(contents);
+}

@@ -588,7 +651,8 @@ static void grab_sub_body_contents(struct atom_value *val, int deref, struct obj
                    strcmp(name, "contents") &&
                    strcmp(name, "contents:subject") &&
                    strcmp(name, "contents:body") &&
-                   strcmp(name, "contents:signature"))
+                   strcmp(name, "contents:signature") &&
+                   !starts_with(name, "contents:lines="))
                        continue;
                if (!subpos)
                        find_subpos(buf, sz,

@@ -608,6 +672,15 @@ static void grab_sub_body_contents(struct atom_value *val, int deref, struct obj
                        v->s = xmemdupz(sigpos, siglen);
                else if (!strcmp(name, "contents"))
                        v->s = xstrdup(subpos);
+               else if (skip_prefix(name, "contents:lines=", &valp)) {
+                       struct contents *contents = xmalloc(sizeof(struct contents));
+
+                       if (strtoul_ui(valp, 10, &contents->lines))
+                               die(_("positive width expected align:%s"), valp);
+                       hashcpy(contents->oid.hash, obj->sha1);

+                       v->handler = contents_lines_handler;
+                       v->contents = contents;
+               }
        }
 }

diff --git a/t/t6302-for-each-ref-filter.sh b/t/t6302-for-each-ref-filter.sh
index cef7a41..0277498 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh

@@ -166,4 +166,20 @@ test_expect_success 'nested alignment' '
        test_cmp expect actual
 '

+test_expect_success 'check `%(contents:lines=X)`' '
+       cat >expect <<-\EOF &&
+       master three
+       side four
+       odd/spot three
+       double-tag Annonated doubly
+       four four
+       one one
+       signed-tag A signed tag message
+       three three
+       two two
+       EOF
+       git for-each-ref --format="%(refname:short) %(contents:lines=1)" >actual &&