Merge branch 'jk/refspecs-negative'

"git fetch" and "git push" support negative refspecs.

* jk/refspecs-negative:
  refspec: add support for negative refspecs

Documentation/pull-fetch-param.txt

@@ -30,6 +30,22 @@ The colon can be omitted when <dst> is empty.  <src> is
 typically a ref, but it can also be a fully spelled hex object
 name.
 +
+A <refspec> may contain a `*` in its <src> to indicate a simple pattern
+match. Such a refspec functions like a glob that matches any ref with the
+same prefix. A pattern <refspec> must have a `*` in both the <src> and
+<dst>. It will map refs to the destination by replacing the `*` with the
+contents matched from the source.
++
+If a refspec is prefixed by `^`, it will be interpreted as a negative
+refspec. Rather than specifying which refs to fetch or which local refs to
+update, such a refspec will instead specify refs to exclude. A ref will be
+considered to match if it matches at least one positive refspec, and does
+not match any negative refspec. Negative refspecs can be useful to restrict
+the scope of a pattern refspec so that it will not include specific refs.
+Negative refspecs can themselves be pattern refspecs. However, they may only
+contain a <src> and do not specify a <dst>. Fully spelled out hex object
+names are also not supported.
++
 `tag <tag>` means the same as `refs/tags/<tag>:refs/tags/<tag>`;
 it requests fetching everything up to the given tag.
 +

builtin/fetch.c

@@ -539,6 +539,16 @@ static struct ref *get_ref_map(struct remote *remote,
 		tail = &rm->next;
 	}
 
+	/*
+	 * apply negative refspecs first, before we remove duplicates. This is
+	 * necessary as negative refspecs might remove an otherwise conflicting
+	 * duplicate.
+	 */
+	if (rs->nr)
+		ref_map = apply_negative_refspecs(ref_map, rs);
+	else
+		ref_map = apply_negative_refspecs(ref_map, &remote->fetch);
+
 	ref_map = ref_remove_duplicates(ref_map);
 
 	for (rm = ref_map; rm; rm = rm->next) {

refspec.c

@@ -8,6 +8,7 @@ static struct refspec_item s_tag_refspec = {
 	1,
 	0,
 	0,
+	0,
 	"refs/tags/*",
 	"refs/tags/*"
 };
@@ -32,10 +33,17 @@ static int parse_refspec(struct refspec_item *item, const char *refspec, int fet
 	if (*lhs == '+') {
 		item->force = 1;
 		lhs++;
+	} else if (*lhs == '^') {
+		item->negative = 1;
+		lhs++;
 	}
 
 	rhs = strrchr(lhs, ':');
 
+	/* negative refspecs only have one side */
+	if (item->negative && rhs)
+		return 0;
+
 	/*
 	 * Before going on, special case ":" (or "+:") as a refspec
 	 * for pushing matching refs.
@@ -55,7 +63,7 @@ static int parse_refspec(struct refspec_item *item, const char *refspec, int fet
 
 	llen = (rhs ? (rhs - lhs - 1) : strlen(lhs));
 	if (1 <= llen && memchr(lhs, '*', llen)) {
-		if ((rhs && !is_glob) || (!rhs && fetch))
+		if ((rhs && !is_glob) || (!rhs && !item->negative && fetch))
 			return 0;
 		is_glob = 1;
 	} else if (rhs && is_glob) {
@@ -66,6 +74,28 @@ static int parse_refspec(struct refspec_item *item, const char *refspec, int fet
 	item->src = xstrndup(lhs, llen);
 	flags = REFNAME_ALLOW_ONELEVEL | (is_glob ? REFNAME_REFSPEC_PATTERN : 0);
 
+	if (item->negative) {
+		struct object_id unused;
+
+		/*
+		 * Negative refspecs only have a LHS, which indicates a ref
+		 * (or pattern of refs) to exclude from other matches. This
+		 * can either be a simple ref, or a glob pattern. Exact sha1
+		 * match is not currently supported.
+		 */
+		if (!*item->src)
+			return 0; /* negative refspecs must not be empty */
+		else if (llen == the_hash_algo->hexsz && !get_oid_hex(item->src, &unused))
+			return 0; /* negative refpsecs cannot be exact sha1 */
+		else if (!check_refname_format(item->src, flags))
+			; /* valid looking ref is ok */
+		else
+			return 0;
+
+		/* the other rules below do not apply to negative refspecs */
+		return 1;
+	}
+
 	if (fetch) {
 		struct object_id unused;
 
@@ -223,7 +253,7 @@ void refspec_ref_prefixes(const struct refspec *rs,
 		const struct refspec_item *item = &rs->items[i];
 		const char *prefix = NULL;
 
-		if (item->exact_sha1)
+		if (item->exact_sha1 || item->negative)
 			continue;
 		if (rs->fetch == REFSPEC_FETCH)
 			prefix = item->src;

refspec.h

@@ -5,12 +5,13 @@
 extern const struct refspec_item *tag_refspec;
 
 /**
- * A struct refspec_item holds the parsed interpretation of a refspec.  If it will
- * force updates (starts with a '+'), force is true.  If it is a pattern
- * (sides end with '*') pattern is true.  src and dest are the two sides
- * (including '*' characters if present); if there is only one side, it is src,
- * and dst is NULL; if sides exist but are empty (i.e., the refspec either
- * starts or ends with ':'), the corresponding side is "".
+ * A struct refspec_item holds the parsed interpretation of a refspec.  If it
+ * will force updates (starts with a '+'), force is true.  If it is a pattern
+ * (sides end with '*') pattern is true.  If it is a negative refspec, (starts
+ * with '^'), negative is true.  src and dest are the two sides (including '*'
+ * characters if present); if there is only one side, it is src, and dst is
+ * NULL; if sides exist but are empty (i.e., the refspec either starts or ends
+ * with ':'), the corresponding side is "".
  *
  * remote_find_tracking(), given a remote and a struct refspec_item with either src
  * or dst filled out, will fill out the other such that the result is in the
@@ -22,6 +23,7 @@ struct refspec_item {
 	unsigned pattern : 1;
 	unsigned matching : 1;
 	unsigned exact_sha1 : 1;
+	unsigned negative : 1;
 
 	char *src;
 	char *dst;

remote.c

@@ -682,6 +682,91 @@ static int match_name_with_pattern(const char *key, const char *name,
 	return ret;
 }
 
+static int refspec_match(const struct refspec_item *refspec,
+			 const char *name)
+{
+	if (refspec->pattern)
+		return match_name_with_pattern(refspec->src, name, NULL, NULL);
+
+	return !strcmp(refspec->src, name);
+}
+
+static int omit_name_by_refspec(const char *name, struct refspec *rs)
+{
+	int i;
+
+	for (i = 0; i < rs->nr; i++) {
+		if (rs->items[i].negative && refspec_match(&rs->items[i], name))
+			return 1;
+	}
+	return 0;
+}
+
+struct ref *apply_negative_refspecs(struct ref *ref_map, struct refspec *rs)
+{
+	struct ref **tail;
+
+	for (tail = &ref_map; *tail; ) {
+		struct ref *ref = *tail;
+
+		if (omit_name_by_refspec(ref->name, rs)) {
+			*tail = ref->next;
+			free(ref->peer_ref);
+			free(ref);
+		} else
+			tail = &ref->next;
+	}
+
+	return ref_map;
+}
+
+static int query_matches_negative_refspec(struct refspec *rs, struct refspec_item *query)
+{
+	int i, matched_negative = 0;
+	int find_src = !query->src;
+	struct string_list reversed = STRING_LIST_INIT_NODUP;
+	const char *needle = find_src ? query->dst : query->src;
+
+	/*
+	 * Check whether the queried ref matches any negative refpsec. If so,
+	 * then we should ultimately treat this as not matching the query at
+	 * all.
+	 *
+	 * Note that negative refspecs always match the source, but the query
+	 * item uses the destination. To handle this, we apply pattern
+	 * refspecs in reverse to figure out if the query source matches any
+	 * of the negative refspecs.
+	 */
+	for (i = 0; i < rs->nr; i++) {
+		struct refspec_item *refspec = &rs->items[i];
+		char *expn_name;
+
+		if (refspec->negative)
+			continue;
+
+		/* Note the reversal of src and dst */
+		if (refspec->pattern) {
+			const char *key = refspec->dst ? refspec->dst : refspec->src;
+			const char *value = refspec->src;
+
+			if (match_name_with_pattern(key, needle, value, &expn_name))
+				string_list_append_nodup(&reversed, expn_name);
+		} else {
+			if (!strcmp(needle, refspec->src))
+				string_list_append(&reversed, refspec->src);
+		}
+	}
+
+	for (i = 0; !matched_negative && i < reversed.nr; i++) {
+		if (omit_name_by_refspec(reversed.items[i].string, rs))
+			matched_negative = 1;
+	}
+
+	string_list_clear(&reversed, 0);
+
+	return matched_negative;
+}
+
 static void query_refspecs_multiple(struct refspec *rs,
 				    struct refspec_item *query,
 				    struct string_list *results)
@@ -692,6 +777,9 @@ static void query_refspecs_multiple(struct refspec *rs,
 	if (find_src && !query->dst)
 		BUG("query_refspecs_multiple: need either src or dst");
 
+	if (query_matches_negative_refspec(rs, query))
+		return;
+
 	for (i = 0; i < rs->nr; i++) {
 		struct refspec_item *refspec = &rs->items[i];
 		const char *key = find_src ? refspec->dst : refspec->src;
@@ -699,7 +787,7 @@ static void query_refspecs_multiple(struct refspec *rs,
 		const char *needle = find_src ? query->dst : query->src;
 		char **result = find_src ? &query->src : &query->dst;
 
-		if (!refspec->dst)
+		if (!refspec->dst || refspec->negative)
 			continue;
 		if (refspec->pattern) {
 			if (match_name_with_pattern(key, needle, value, result))
@@ -720,12 +808,15 @@ int query_refspecs(struct refspec *rs, struct refspec_item *query)
 	if (find_src && !query->dst)
 		BUG("query_refspecs: need either src or dst");
 
+	if (query_matches_negative_refspec(rs, query))
+		return -1;
+
 	for (i = 0; i < rs->nr; i++) {
 		struct refspec_item *refspec = &rs->items[i];
 		const char *key = find_src ? refspec->dst : refspec->src;
 		const char *value = find_src ? refspec->src : refspec->dst;
 
-		if (!refspec->dst)
+		if (!refspec->dst || refspec->negative)
 			continue;
 		if (refspec->pattern) {
 			if (match_name_with_pattern(key, needle, value, result)) {
@@ -1054,7 +1145,7 @@ static int match_explicit(struct ref *src, struct ref *dst,
 	const char *dst_value = rs->dst;
 	char *dst_guess;
 
-	if (rs->pattern || rs->matching)
+	if (rs->pattern || rs->matching || rs->negative)
 		return 0;
 
 	matched_src = matched_dst = NULL;
@@ -1130,6 +1221,10 @@ static char *get_ref_match(const struct refspec *rs, const struct ref *ref,
 	int matching_refs = -1;
 	for (i = 0; i < rs->nr; i++) {
 		const struct refspec_item *item = &rs->items[i];
+
+		if (item->negative)
+			continue;
+
 		if (item->matching &&
 		    (matching_refs == -1 || item->force)) {
 			matching_refs = i;
@@ -1335,7 +1430,7 @@ int check_push_refs(struct ref *src, struct refspec *rs)
 	for (i = 0; i < rs->nr; i++) {
 		struct refspec_item *item = &rs->items[i];
 
-		if (item->pattern || item->matching)
+		if (item->pattern || item->matching || item->negative)
 			continue;
 
 		ret |= match_explicit_lhs(src, item, NULL, NULL);
@@ -1437,6 +1532,8 @@ int match_push_refs(struct ref *src, struct ref **dst,
 		string_list_clear(&src_ref_index, 0);
 	}
 
+	*dst = apply_negative_refspecs(*dst, rs);
+
 	if (errs)
 		return -1;
 	return 0;
@@ -1806,6 +1903,9 @@ int get_fetch_map(const struct ref *remote_refs,
 {
 	struct ref *ref_map, **rmp;
 
+	if (refspec->negative)
+		return 0;
+
 	if (refspec->pattern) {
 		ref_map = get_expanded_map(remote_refs, refspec);
 	} else {

remote.h

@@ -202,6 +202,12 @@ int resolve_remote_symref(struct ref *ref, struct ref *list);
  */
 struct ref *ref_remove_duplicates(struct ref *ref_map);
 
+/*
+ * Remove all entries in the input list which match any negative refspec in
+ * the refspec list.
+ */
+struct ref *apply_negative_refspecs(struct ref *ref_map, struct refspec *rs);
+
 int query_refspecs(struct refspec *rs, struct refspec_item *query);
 char *apply_refspecs(struct refspec *rs, const char *name);
 
@@ -214,7 +220,8 @@ void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 /*
  * Given a list of the remote refs and the specification of things to
  * fetch, makes a (separate) list of the refs to fetch and the local
- * refs to store into.
+ * refs to store into. Note that negative refspecs are ignored here, and
+ * should be handled separately.
  *
  * *tail is the pointer to the tail pointer of the list of results
  * beforehand, and will be set to the tail pointer of the list of

t/t5582-fetch-negative-refspec.sh

@@ -0,0 +1,189 @@
+#!/bin/sh
+# Copyright (c) 2020, Jacob Keller.
+
+test_description='"git fetch" with negative refspecs.
+
+'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	echo >file original &&
+	git add file &&
+	git commit -a -m original
+'
+
+test_expect_success "clone and setup child repos" '
+	git clone . one &&
+	(
+		cd one &&
+		echo >file updated by one &&
+		git commit -a -m "updated by one" &&
+		git switch -c alternate &&
+		echo >file updated again by one &&
+		git commit -a -m "updated by one again" &&
+		git switch master
+	) &&
+	git clone . two &&
+	(
+		cd two &&
+		git config branch.master.remote one &&
+		git config remote.one.url ../one/.git/ &&
+		git config remote.one.fetch +refs/heads/*:refs/remotes/one/* &&
+		git config --add remote.one.fetch ^refs/heads/alternate
+	) &&
+	git clone . three
+'
+
+test_expect_success "fetch one" '
+	echo >file updated by origin &&
+	git commit -a -m "updated by origin" &&
+	(
+		cd two &&
+		test_must_fail git rev-parse --verify refs/remotes/one/alternate &&
+		git fetch one &&
+		test_must_fail git rev-parse --verify refs/remotes/one/alternate &&
+		git rev-parse --verify refs/remotes/one/master &&
+		mine=$(git rev-parse refs/remotes/one/master) &&
+		his=$(cd ../one && git rev-parse refs/heads/master) &&
+		test "z$mine" = "z$his"
+	)
+'
+
+test_expect_success "fetch with negative refspec on commandline" '
+	echo >file updated by origin again &&
+	git commit -a -m "updated by origin again" &&
+	(
+		cd three &&
+		alternate_in_one=$(cd ../one && git rev-parse refs/heads/alternate) &&
+		echo $alternate_in_one >expect &&
+		git fetch ../one/.git refs/heads/*:refs/remotes/one/* ^refs/heads/master &&
+		cut -f -1 .git/FETCH_HEAD >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "fetch with negative sha1 refspec fails" '
+	echo >file updated by origin yet again &&
+	git commit -a -m "updated by origin yet again" &&
+	(
+		cd three &&
+		master_in_one=$(cd ../one && git rev-parse refs/heads/master) &&
+		test_must_fail git fetch ../one/.git refs/heads/*:refs/remotes/one/* ^$master_in_one
+	)
+'
+
+test_expect_success "fetch with negative pattern refspec" '
+	echo >file updated by origin once more &&
+	git commit -a -m "updated by origin once more" &&
+	(
+		cd three &&
+		alternate_in_one=$(cd ../one && git rev-parse refs/heads/alternate) &&
+		echo $alternate_in_one >expect &&
+		git fetch ../one/.git refs/heads/*:refs/remotes/one/* ^refs/heads/m* &&
+		cut -f -1 .git/FETCH_HEAD >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "fetch with negative pattern refspec does not expand prefix" '
+	echo >file updated by origin another time &&
+	git commit -a -m "updated by origin another time" &&
+	(
+		cd three &&
+		alternate_in_one=$(cd ../one && git rev-parse refs/heads/alternate) &&
+		master_in_one=$(cd ../one && git rev-parse refs/heads/master) &&
+		echo $alternate_in_one >expect &&
+		echo $master_in_one >>expect &&
+		git fetch ../one/.git refs/heads/*:refs/remotes/one/* ^master &&
+		cut -f -1 .git/FETCH_HEAD >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "fetch with negative refspec avoids duplicate conflict" '
+	cd "$D" &&
+	(
+		cd one &&
+		git branch dups/a &&
+		git branch dups/b &&
+		git branch dups/c &&
+		git branch other/a &&
+		git rev-parse --verify refs/heads/other/a >../expect &&
+		git rev-parse --verify refs/heads/dups/b >>../expect &&
+		git rev-parse --verify refs/heads/dups/c >>../expect
+	) &&
+	(
+		cd three &&
+		git fetch ../one/.git ^refs/heads/dups/a refs/heads/dups/*:refs/dups/* refs/heads/other/a:refs/dups/a &&
+		git rev-parse --verify refs/dups/a >../actual &&
+		git rev-parse --verify refs/dups/b >>../actual &&
+		git rev-parse --verify refs/dups/c >>../actual
+	) &&
+	test_cmp expect actual
+'
+
+test_expect_success "push --prune with negative refspec" '
+	(
+		cd two &&
+		git branch prune/a &&
+		git branch prune/b &&
+		git branch prune/c &&
+		git push ../three refs/heads/prune/* &&
+		git branch -d prune/a &&
+		git branch -d prune/b &&
+		git push --prune ../three refs/heads/prune/* ^refs/heads/prune/b
+	) &&
+	(
+		cd three &&
+		test_write_lines b c >expect &&
+		git for-each-ref --format="%(refname:lstrip=3)" refs/heads/prune/ >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "push --prune with negative refspec apply to the destination" '
+	(
+		cd two &&
+		git branch ours/a &&
+		git branch ours/b &&
+		git branch ours/c &&
+		git push ../three refs/heads/ours/*:refs/heads/theirs/* &&
+		git branch -d ours/a &&
+		git branch -d ours/b &&
+		git push --prune ../three refs/heads/ours/*:refs/heads/theirs/* ^refs/heads/theirs/b
+	) &&
+	(
+		cd three &&
+		test_write_lines b c >expect &&
+		git for-each-ref --format="%(refname:lstrip=3)" refs/heads/theirs/ >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success "fetch --prune with negative refspec" '
+	(
+		cd two &&
+		git branch fetch/a &&
+		git branch fetch/b &&
+		git branch fetch/c
+	) &&
+	(
+		cd three &&
+		git fetch ../two/.git refs/heads/fetch/*:refs/heads/copied/*
+	) &&
+	(
+		cd two &&
+		git branch -d fetch/a &&
+		git branch -d fetch/b
+	) &&
+	(
+		cd three &&
+		test_write_lines b c >expect &&
+		git fetch -v ../two/.git --prune refs/heads/fetch/*:refs/heads/copied/* ^refs/heads/fetch/b &&
+		git for-each-ref --format="%(refname:lstrip=3)" refs/heads/copied/ >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_done