[PATCH v4 6/8] ref-filter: add `short` modifier to 'parent' atom

["Hariom Verma via GitGitGadget" <gitgitgadget@gmail.com>]

From: Hariom Verma <hariom18599@gmail.com>

Sometimes while using 'parent' atom, user might want to see abbrev hash
instead of full 40 character hash.

Just like 'objectname', it might be convenient for users to have the
`:short` and `:short=<length>` option for printing 'parent' hash.

Let's introduce `short` option to 'parent' atom.

Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Mentored-by: Heba Waly <heba.waly@gmail.com>
Signed-off-by: Hariom Verma <hariom18599@gmail.com>
---
 Documentation/git-for-each-ref.txt | 2 +-
 ref-filter.c                       | 8 ++++----
 t/t6300-for-each-ref.sh            | 6 ++++++
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index 40ebdfcc41..dd09763e7d 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -222,7 +222,7 @@ worktreepath::
 In addition to the above, for commit and tag objects, the header
 field names (`tree`, `parent`, `object`, `type`, and `tag`) can
 be used to specify the value in the header field.
-Field `tree` can also be used with modifier `:short` and
+Fields `tree` and `parent` can also be used with modifier `:short` and
 `:short=<length>` just like `objectname`.
 
 For commit and tag objects, the special `creatordate` and `creator`
diff --git a/ref-filter.c b/ref-filter.c
index 3449fe45d8..c7d81088e4 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -498,7 +498,7 @@ static struct {
 	{ "objectname", SOURCE_OTHER, FIELD_STR, oid_atom_parser },
 	{ "deltabase", SOURCE_OTHER, FIELD_STR, deltabase_atom_parser },
 	{ "tree", SOURCE_OBJ, FIELD_STR, oid_atom_parser },
-	{ "parent", SOURCE_OBJ },
+	{ "parent", SOURCE_OBJ, FIELD_STR, oid_atom_parser },
 	{ "numparent", SOURCE_OBJ, FIELD_ULONG },
 	{ "object", SOURCE_OBJ },
 	{ "type", SOURCE_OBJ },
@@ -1011,14 +1011,14 @@ static void grab_commit_values(struct atom_value *val, int deref, struct object
 			v->value = commit_list_count(commit->parents);
 			v->s = xstrfmt("%lu", (unsigned long)v->value);
 		}
-		else if (!strcmp(name, "parent")) {
+		else if (starts_with(name, "parent")) {
 			struct commit_list *parents;
 			struct strbuf s = STRBUF_INIT;
 			for (parents = commit->parents; parents; parents = parents->next) {
-				struct commit *parent = parents->item;
+				struct object_id *oid = &parents->item->object.oid;
 				if (parents != commit->parents)
 					strbuf_addch(&s, ' ');
-				strbuf_addstr(&s, oid_to_hex(&parent->object.oid));
+				strbuf_addstr(&s, do_grab_oid("parent", oid, &used_atom[i]));
 			}
 			v->s = strbuf_detach(&s, NULL);
 		}
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index e30bbff6d9..79d5b29387 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -120,6 +120,9 @@ test_atom head tree:short $(git rev-parse --short refs/heads/master^{tree})
 test_atom head tree:short=1 $(git rev-parse --short=1 refs/heads/master^{tree})
 test_atom head tree:short=10 $(git rev-parse --short=10 refs/heads/master^{tree})
 test_atom head parent ''
+test_atom head parent:short ''
+test_atom head parent:short=1 ''
+test_atom head parent:short=10 ''
 test_atom head numparent 0
 test_atom head object ''
 test_atom head type ''
@@ -174,6 +177,9 @@ test_atom tag tree:short ''
 test_atom tag tree:short=1 ''
 test_atom tag tree:short=10 ''
 test_atom tag parent ''
+test_atom tag parent:short ''
+test_atom tag parent:short=1 ''
+test_atom tag parent:short=10 ''
 test_atom tag numparent ''
 test_atom tag object $(git rev-parse refs/tags/testtag^0)
 test_atom tag type 'commit'
-- 
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