Backport negative refspec patches

include/git2/refspec.h

@@ -79,7 +79,16 @@ GIT_EXTERN(int) git_refspec_force(const git_refspec *refspec);
 GIT_EXTERN(git_direction) git_refspec_direction(const git_refspec *spec);
 
 /**
- * Check if a refspec's source descriptor matches a reference 
+ * Check if a refspec's source descriptor matches a negative reference
+ *
+ * @param refspec the refspec
+ * @param refname the name of the reference to check
+ * @return 1 if the refspec matches, 0 otherwise
+ */
+GIT_EXTERN(int) git_refspec_src_matches_negative(const git_refspec *refspec, const char *refname);
+
+/**
+ * Check if a refspec's source descriptor matches a reference
  *
  * @param refspec the refspec
  * @param refname the name of the reference to check

src/refs.c

@@ -813,17 +813,20 @@ static int is_valid_ref_char(char ch)
 	}
 }
 
-static int ensure_segment_validity(const char *name, char may_contain_glob)
+static int ensure_segment_validity(const char *name, char may_contain_glob, bool allow_caret_prefix)
 {
 	const char *current = name;
+	const char *start = current;
 	char prev = '\0';
 	const int lock_len = (int)strlen(GIT_FILELOCK_EXTENSION);
 	int segment_len;
 
 	if (*current == '.')
 		return -1; /* Refname starts with "." */
+	if (allow_caret_prefix && *current == '^')
+		start++;
 
-	for (current = name; ; current++) {
+	for (current = start; ; current++) {
 		if (*current == '\0' || *current == '/')
 			break;
 
@@ -855,7 +858,7 @@ static int ensure_segment_validity(const char *name, char may_contain_glob)
 	return segment_len;
 }
 
-static bool is_all_caps_and_underscore(const char *name, size_t len)
+static bool is_valid_normalized_name(const char *name, size_t len)
 {
 	size_t i;
 	char c;
@@ -865,6 +868,9 @@ static bool is_all_caps_and_underscore(const char *name, size_t len)
 	for (i = 0; i < len; i++)
 	{
 		c = name[i];
+		if (i == 0 && c == '^')
+			continue; /* The first character is allowed to be "^" for negative refspecs */
+
 		if ((c < 'A' || c > 'Z') && c != '_')
 			return false;
 	}
@@ -885,6 +891,7 @@ int git_reference__normalize_name(
 	int segment_len, segments_count = 0, error = GIT_EINVALIDSPEC;
 	unsigned int process_flags;
 	bool normalize = (buf != NULL);
+	bool allow_caret_prefix = true;
 	bool validate = (flags & GIT_REFERENCE_FORMAT__VALIDATION_DISABLE) == 0;
 
 #ifdef GIT_USE_ICONV
@@ -922,7 +929,7 @@ int git_reference__normalize_name(
 	while (true) {
 		char may_contain_glob = process_flags & GIT_REFERENCE_FORMAT_REFSPEC_PATTERN;
 
-		segment_len = ensure_segment_validity(current, may_contain_glob);
+		segment_len = ensure_segment_validity(current, may_contain_glob, allow_caret_prefix);
 		if (segment_len < 0)
 			goto cleanup;
 
@@ -958,6 +965,12 @@ int git_reference__normalize_name(
 			break;
 
 		current += segment_len + 1;
+
+		/*
+		 * A caret prefix is only allowed in the first segment to signify a
+		 * negative refspec.
+		 */
+		allow_caret_prefix = false;
 	}
 
 	/* A refname can not be empty */
@@ -977,12 +990,12 @@ int git_reference__normalize_name(
 
 	if ((segments_count == 1 ) &&
 	    !(flags & GIT_REFERENCE_FORMAT_REFSPEC_SHORTHAND) &&
-		!(is_all_caps_and_underscore(name, (size_t)segment_len) ||
+		!(is_valid_normalized_name(name, (size_t)segment_len) ||
 			((flags & GIT_REFERENCE_FORMAT_REFSPEC_PATTERN) && !strcmp("*", name))))
 			goto cleanup;
 
 	if ((segments_count > 1)
-		&& (is_all_caps_and_underscore(name, strchr(name, '/') - name)))
+		&& (is_valid_normalized_name(name, strchr(name, '/') - name)))
 			goto cleanup;
 
 	error = 0;

src/refspec.c

@@ -22,6 +22,7 @@ int git_refspec__parse(git_refspec *refspec, const char *input, bool is_fetch)
 	int is_glob = 0;
 	const char *lhs, *rhs;
 	int flags;
+	bool is_neg_refspec = false;
 
 	assert(refspec && input);
 
@@ -33,6 +34,9 @@ int git_refspec__parse(git_refspec *refspec, const char *input, bool is_fetch)
 		refspec->force = 1;
 		lhs++;
 	}
+	if (*lhs == '^') {
+		is_neg_refspec = true;
+	}
 
 	rhs = strrchr(lhs, ':');
 
@@ -61,7 +65,14 @@ int git_refspec__parse(git_refspec *refspec, const char *input, bool is_fetch)
 
 	llen = (rhs ? (size_t)(rhs - lhs - 1) : strlen(lhs));
 	if (1 <= llen && memchr(lhs, '*', llen)) {
-		if ((rhs && !is_glob) || (!rhs && is_fetch))
+		/*
+		 * If the lefthand side contains a glob, then one of the following must be
+		 * true, otherwise the spec is invalid
+		 *   1) the rhs exists and also contains a glob
+		 *   2) it is a negative refspec (i.e. no rhs)
+		 *   3) the rhs doesn't exist and we're fetching
+		 */
+		if ((rhs && !is_glob) || (rhs && is_neg_refspec) || (!rhs && is_fetch && !is_neg_refspec))
 			goto invalid;
 		is_glob = 1;
 	} else if (rhs && is_glob)
@@ -208,6 +219,14 @@ int git_refspec_force(const git_refspec *refspec)
 	return refspec->force;
 }
 
+int git_refspec_src_matches_negative(const git_refspec *refspec, const char *refname)
+{
+	if (refspec == NULL || refspec->src == NULL || !git_refspec_is_negative(refspec))
+		return false;
+
+	return (wildmatch(refspec->src + 1, refname, 0) == 0);
+}
+
 int git_refspec_src_matches(const git_refspec *refspec, const char *refname)
 {
 	if (refspec == NULL || refspec->src == NULL)
@@ -216,6 +235,14 @@ int git_refspec_src_matches(const git_refspec *refspec, const char *refname)
 	return (wildmatch(refspec->src, refname, 0) == 0);
 }
 
+int git_refspec_is_negative(const git_refspec *spec)
+{
+	GIT_ASSERT_ARG(spec);
+	GIT_ASSERT_ARG(spec->src);
+
+	return (spec->src[0] == '^' && spec->dst == NULL);
+}
+
 int git_refspec_dst_matches(const git_refspec *refspec, const char *refname)
 {
 	if (refspec == NULL || refspec->dst == NULL)

src/refspec.h

@@ -42,6 +42,14 @@ int git_refspec__serialize(git_buf *out, const git_refspec *refspec);
  */
 int git_refspec_is_wildcard(const git_refspec *spec);
 
+/**
+ * Determines if a refspec is a negative refspec.
+ *
+ * @param spec the refspec
+ * @return 1 if the refspec is a negative, 0 otherwise
+ */
+int git_refspec_is_negative(const git_refspec *spec);
+
 /**
  * DWIM `spec` with `refs` existing on the remote, append the dwim'ed
  * result in `out`.

src/remote.c

@@ -2112,17 +2112,21 @@ int git_remote_is_valid_name(
 git_refspec *git_remote__matching_refspec(git_remote *remote, const char *refname)
 {
 	git_refspec *spec;
+	git_refspec *match = NULL;
 	size_t i;
 
 	git_vector_foreach(&remote->active_refspecs, i, spec) {
 		if (spec->push)
 			continue;
 
+		if (git_refspec_is_negative(spec) && git_refspec_src_matches_negative(spec, refname))
+			return NULL;
+
 		if (git_refspec_src_matches(spec, refname))
-			return spec;
+			match = spec;
 	}
 
-	return NULL;
+	return match;
 }
 
 git_refspec *git_remote__matching_dst_refspec(git_remote *remote, const char *refname)