[PATCH 1/2] refs: expose 'for_each_fullref_in_prefixes'

[Taylor Blau <me@ttaylorr.com>]

This function was used in the ref-filter.c code to find the longest
common prefix of among a set of refspecs, and then to iterate all of the
references that descend from that prefix.

The subsequent patch will want to use that same code from ls-refs, so
prepare by exposing and moving it to refs.c. Since there is nothing
specific to the ref-filter code here (other than that it was previously
the only caller of this function), this really belongs in the more
generic refs.h header.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 ref-filter.c | 74 ++------------------------------------------
 refs.c       | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 refs.h       |  7 +++++
 3 files changed, 96 insertions(+), 72 deletions(-)

diff --git a/ref-filter.c b/ref-filter.c
index aa260bfd09..f918f00151 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -1929,64 +1929,6 @@ static int filter_pattern_match(struct ref_filter *filter, const char *refname)
 	return match_pattern(filter, refname);
 }
 
-static int qsort_strcmp(const void *va, const void *vb)
-{
-	const char *a = *(const char **)va;
-	const char *b = *(const char **)vb;
-
-	return strcmp(a, b);
-}
-
-static void find_longest_prefixes_1(struct string_list *out,
-				  struct strbuf *prefix,
-				  const char **patterns, size_t nr)
-{
-	size_t i;
-
-	for (i = 0; i < nr; i++) {
-		char c = patterns[i][prefix->len];
-		if (!c || is_glob_special(c)) {
-			string_list_append(out, prefix->buf);
-			return;
-		}
-	}
-
-	i = 0;
-	while (i < nr) {
-		size_t end;
-
-		/*
-		* Set "end" to the index of the element _after_ the last one
-		* in our group.
-		*/
-		for (end = i + 1; end < nr; end++) {
-			if (patterns[i][prefix->len] != patterns[end][prefix->len])
-				break;
-		}
-
-		strbuf_addch(prefix, patterns[i][prefix->len]);
-		find_longest_prefixes_1(out, prefix, patterns + i, end - i);
-		strbuf_setlen(prefix, prefix->len - 1);
-
-		i = end;
-	}
-}
-
-static void find_longest_prefixes(struct string_list *out,
-				  const char **patterns)
-{
-	struct strvec sorted = STRVEC_INIT;
-	struct strbuf prefix = STRBUF_INIT;
-
-	strvec_pushv(&sorted, patterns);
-	QSORT(sorted.v, sorted.nr, qsort_strcmp);
-
-	find_longest_prefixes_1(out, &prefix, sorted.v, sorted.nr);
-
-	strvec_clear(&sorted);
-	strbuf_release(&prefix);
-}
-
 /*
  * This is the same as for_each_fullref_in(), but it tries to iterate
  * only over the patterns we'll care about. Note that it _doesn't_ do a full
@@ -1997,10 +1939,6 @@ static int for_each_fullref_in_pattern(struct ref_filter *filter,
 				       void *cb_data,
 				       int broken)
 {
-	struct string_list prefixes = STRING_LIST_INIT_DUP;
-	struct string_list_item *prefix;
-	int ret;
-
 	if (!filter->match_as_path) {
 		/*
 		 * in this case, the patterns are applied after
@@ -2024,16 +1962,8 @@ static int for_each_fullref_in_pattern(struct ref_filter *filter,
 		return for_each_fullref_in("", cb, cb_data, broken);
 	}
 
-	find_longest_prefixes(&prefixes, filter->name_patterns);
-
-	for_each_string_list_item(prefix, &prefixes) {
-		ret = for_each_fullref_in(prefix->string, cb, cb_data, broken);
-		if (ret)
-			break;
-	}
-
-	string_list_clear(&prefixes, 0);
-	return ret;
+	return for_each_fullref_in_prefixes(NULL, filter->name_patterns,
+					    cb, cb_data, broken);
 }
 
 /*
diff --git a/refs.c b/refs.c
index 13dc2c3291..0b5a68588f 100644
--- a/refs.c
+++ b/refs.c
@@ -1546,6 +1546,93 @@ int for_each_rawref(each_ref_fn fn, void *cb_data)
 	return refs_for_each_rawref(get_main_ref_store(the_repository), fn, cb_data);
 }
 
+static int qsort_strcmp(const void *va, const void *vb)
+{
+	const char *a = *(const char **)va;
+	const char *b = *(const char **)vb;
+
+	return strcmp(a, b);
+}
+
+static void find_longest_prefixes_1(struct string_list *out,
+				  struct strbuf *prefix,
+				  const char **patterns, size_t nr)
+{
+	size_t i;
+
+	for (i = 0; i < nr; i++) {
+		char c = patterns[i][prefix->len];
+		if (!c || is_glob_special(c)) {
+			string_list_append(out, prefix->buf);
+			return;
+		}
+	}
+
+	i = 0;
+	while (i < nr) {
+		size_t end;
+
+		/*
+		* Set "end" to the index of the element _after_ the last one
+		* in our group.
+		*/
+		for (end = i + 1; end < nr; end++) {
+			if (patterns[i][prefix->len] != patterns[end][prefix->len])
+				break;
+		}
+
+		strbuf_addch(prefix, patterns[i][prefix->len]);
+		find_longest_prefixes_1(out, prefix, patterns + i, end - i);
+		strbuf_setlen(prefix, prefix->len - 1);
+
+		i = end;
+	}
+}
+
+static void find_longest_prefixes(struct string_list *out,
+				  const char **patterns)
+{
+	struct strvec sorted = STRVEC_INIT;
+	struct strbuf prefix = STRBUF_INIT;
+
+	strvec_pushv(&sorted, patterns);
+	QSORT(sorted.v, sorted.nr, qsort_strcmp);
+
+	find_longest_prefixes_1(out, &prefix, sorted.v, sorted.nr);
+
+	strvec_clear(&sorted);
+	strbuf_release(&prefix);
+}
+
+int for_each_fullref_in_prefixes(const char *namespace,
+				 const char **patterns,
+				 each_ref_fn fn, void *cb_data,
+				 unsigned int broken)
+{
+	struct string_list prefixes = STRING_LIST_INIT_DUP;
+	struct string_list_item *prefix;
+	struct strbuf buf = STRBUF_INIT;
+	int ret = 0, namespace_len;
+
+	find_longest_prefixes(&prefixes, patterns);
+
+	if (namespace)
+		strbuf_addstr(&buf, namespace);
+	namespace_len = buf.len;
+
+	for_each_string_list_item(prefix, &prefixes) {
+		strbuf_addf(&buf, "%s", prefix->string);
+		ret = for_each_fullref_in(buf.buf, fn, cb_data, broken);
+		if (ret)
+			break;
+		strbuf_setlen(&buf, namespace_len);
+	}
+
+	string_list_clear(&prefixes, 0);
+	strbuf_release(&buf);
+	return ret;
+}
+
 static int refs_read_special_head(struct ref_store *ref_store,
 				  const char *refname, struct object_id *oid,
 				  struct strbuf *referent, unsigned int *type)
diff --git a/refs.h b/refs.h
index ff05d2e9fe..e88a794ee6 100644
--- a/refs.h
+++ b/refs.h
@@ -347,6 +347,13 @@ int refs_for_each_fullref_in(struct ref_store *refs, const char *prefix,
 int for_each_fullref_in(const char *prefix, each_ref_fn fn, void *cb_data,
 			unsigned int broken);
 
+/**
+ * iterate all refs which are descendent from the longest common prefix among
+ * the list "patterns".
+ */
+int for_each_fullref_in_prefixes(const char *namespace, const char **patterns,
+				 each_ref_fn fn, void *cb_data,
+				 unsigned int broken);
 /**
  * iterate refs from the respective area.
  */
-- 
2.30.0.138.g6d7191ea01