ref-filter: implement '--contains' option

'tag -l' and 'branch -l' have two different ways of finding
out if a certain ref contains a commit. Implement both these
methods in ref-filter and give the caller of ref-filter API
the option to pick which implementation to be used.

'branch -l' uses 'is_descendant_of()' from commit.c which is
left as the default implementation to be used.

'tag -l' uses a more specific algorithm since ffc4b80. This
implementation is used whenever the 'with_commit_tag_algo' bit
is set in 'struct ref_filter'.

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/tag.c b/builtin/tag.c
index 767162e..071d001 100644 (file)
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -86,6 +86,11 @@ static int in_commit_list(const struct commit_list *want, struct commit *c)
        return 0;
 }
 
+/*
+ * The entire code segment for supporting the --contains option has been
+ * copied over to ref-filter.{c,h}. This will be deleted evetually when
+ * we port tag.c to use ref-filter APIs.
+ */
 enum contains_result {
        CONTAINS_UNKNOWN = -1,
        CONTAINS_NO = 0,

diff --git a/ref-filter.c b/ref-filter.c
index 0d7ec44..409b94f 100644 (file)
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -818,6 +818,114 @@ static void get_ref_atom_value(struct ref_array_item *ref, int atom, struct atom
        *v = &ref->value[atom];
 }
 
+enum contains_result {
+       CONTAINS_UNKNOWN = -1,
+       CONTAINS_NO = 0,
+       CONTAINS_YES = 1
+};
+
+/*
+ * Mimicking the real stack, this stack lives on the heap, avoiding stack
+ * overflows.
+ *
+ * At each recursion step, the stack items points to the commits whose
+ * ancestors are to be inspected.
+ */
+struct contains_stack {
+       int nr, alloc;
+       struct contains_stack_entry {
+               struct commit *commit;
+               struct commit_list *parents;
+       } *contains_stack;
+};
+
+static int in_commit_list(const struct commit_list *want, struct commit *c)
+{
+       for (; want; want = want->next)
+               if (!hashcmp(want->item->object.sha1, c->object.sha1))
+                       return 1;
+       return 0;
+}
+
+/*
+ * Test whether the candidate or one of its parents is contained in the list.
+ * Do not recurse to find out, though, but return -1 if inconclusive.
+ */
+static enum contains_result contains_test(struct commit *candidate,
+                           const struct commit_list *want)
+{
+       /* was it previously marked as containing a want commit? */
+       if (candidate->object.flags & TMP_MARK)
+               return 1;
+       /* or marked as not possibly containing a want commit? */
+       if (candidate->object.flags & UNINTERESTING)
+               return 0;
+       /* or are we it? */
+       if (in_commit_list(want, candidate)) {
+               candidate->object.flags |= TMP_MARK;
+               return 1;
+       }
+
+       if (parse_commit(candidate) < 0)
+               return 0;
+
+       return -1;
+}
+
+static void push_to_contains_stack(struct commit *candidate, struct contains_stack *contains_stack)
+{
+       ALLOC_GROW(contains_stack->contains_stack, contains_stack->nr + 1, contains_stack->alloc);
+       contains_stack->contains_stack[contains_stack->nr].commit = candidate;
+       contains_stack->contains_stack[contains_stack->nr++].parents = candidate->parents;
+}
+
+static enum contains_result contains_tag_algo(struct commit *candidate,
+               const struct commit_list *want)
+{
+       struct contains_stack contains_stack = { 0, 0, NULL };
+       int result = contains_test(candidate, want);
+
+       if (result != CONTAINS_UNKNOWN)
+               return result;
+
+       push_to_contains_stack(candidate, &contains_stack);
+       while (contains_stack.nr) {
+               struct contains_stack_entry *entry = &contains_stack.contains_stack[contains_stack.nr - 1];
+               struct commit *commit = entry->commit;
+               struct commit_list *parents = entry->parents;
+
+               if (!parents) {
+                       commit->object.flags |= UNINTERESTING;
+                       contains_stack.nr--;
+               }
+               /*
+                * If we just popped the stack, parents->item has been marked,
+                * therefore contains_test will return a meaningful 0 or 1.
+                */
+               else switch (contains_test(parents->item, want)) {
+               case CONTAINS_YES:
+                       commit->object.flags |= TMP_MARK;
+                       contains_stack.nr--;
+                       break;
+               case CONTAINS_NO:
+                       entry->parents = parents->next;
+                       break;
+               case CONTAINS_UNKNOWN:
+                       push_to_contains_stack(parents->item, &contains_stack);
+                       break;
+               }
+       }
+       free(contains_stack.contains_stack);
+       return contains_test(candidate, want);
+}
+
+static int commit_contains(struct ref_filter *filter, struct commit *commit)
+{
+       if (filter->with_commit_tag_algo)
+               return contains_tag_algo(commit, filter->with_commit);
+       return is_descendant_of(commit, filter->with_commit);
+}
+
 /*
  * Return 1 if the refname matches one of the patterns, otherwise 0.
  * A pattern can be path prefix (e.g. a refname "refs/heads/master"
@@ -917,10 +1025,14 @@ static int ref_filter_handler(const char *refname, const struct object_id *oid,
         * obtain the commit using the 'oid' available and discard all
         * non-commits early. The actual filtering is done later.
         */
-       if (filter->merge_commit) {
+       if (filter->merge_commit || filter->with_commit) {
                commit = lookup_commit_reference_gently(oid->hash, 1);
                if (!commit)
                        return 0;
+               /* We perform the filtering for the '--contains' option */
+               if (filter->with_commit &&
+                   !commit_contains(filter, commit))
+                       return 0;
        }
 
        /*

diff --git a/ref-filter.h b/ref-filter.h
index f115174..6bf27d8 100644 (file)
--- a/ref-filter.h
+++ b/ref-filter.h
@@ -44,6 +44,7 @@ struct ref_array {
 struct ref_filter {
        const char **name_patterns;
        struct sha1_array points_at;
+       struct commit_list *with_commit;
 
        enum {
                REF_FILTER_MERGED_NONE = 0,
@@ -51,6 +52,8 @@ struct ref_filter {
                REF_FILTER_MERGED_OMIT
        } merge;
        struct commit *merge_commit;
+
+       unsigned int with_commit_tag_algo : 1;
 };
 
 struct ref_filter_cbdata {