refspec: move refspec parsing logic into its own file

In preparation for performing a refactor on refspec related code, move
the refspec parsing logic into its own file.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refspec.c

@@ -0,0 +1,167 @@
+#include "cache.h"
+#include "refs.h"
+#include "refspec.h"
+
+static struct refspec s_tag_refspec = {
+	0,
+	1,
+	0,
+	0,
+	"refs/tags/*",
+	"refs/tags/*"
+};
+
+/* See TAG_REFSPEC for the string version */
+const struct refspec *tag_refspec = &s_tag_refspec;
+
+static struct refspec *parse_refspec_internal(int nr_refspec, const char **refspec, int fetch, int verify)
+{
+	int i;
+	struct refspec *rs = xcalloc(nr_refspec, sizeof(*rs));
+
+	for (i = 0; i < nr_refspec; i++) {
+		size_t llen;
+		int is_glob;
+		const char *lhs, *rhs;
+		int flags;
+
+		is_glob = 0;
+
+		lhs = refspec[i];
+		if (*lhs == '+') {
+			rs[i].force = 1;
+			lhs++;
+		}
+
+		rhs = strrchr(lhs, ':');
+
+		/*
+		 * Before going on, special case ":" (or "+:") as a refspec
+		 * for pushing matching refs.
+		 */
+		if (!fetch && rhs == lhs && rhs[1] == '\0') {
+			rs[i].matching = 1;
+			continue;
+		}
+
+		if (rhs) {
+			size_t rlen = strlen(++rhs);
+			is_glob = (1 <= rlen && strchr(rhs, '*'));
+			rs[i].dst = xstrndup(rhs, rlen);
+		}
+
+		llen = (rhs ? (rhs - lhs - 1) : strlen(lhs));
+		if (1 <= llen && memchr(lhs, '*', llen)) {
+			if ((rhs && !is_glob) || (!rhs && fetch))
+				goto invalid;
+			is_glob = 1;
+		} else if (rhs && is_glob) {
+			goto invalid;
+		}
+
+		rs[i].pattern = is_glob;
+		rs[i].src = xstrndup(lhs, llen);
+		flags = REFNAME_ALLOW_ONELEVEL | (is_glob ? REFNAME_REFSPEC_PATTERN : 0);
+
+		if (fetch) {
+			struct object_id unused;
+
+			/* LHS */
+			if (!*rs[i].src)
+				; /* empty is ok; it means "HEAD" */
+			else if (llen == GIT_SHA1_HEXSZ && !get_oid_hex(rs[i].src, &unused))
+				rs[i].exact_sha1 = 1; /* ok */
+			else if (!check_refname_format(rs[i].src, flags))
+				; /* valid looking ref is ok */
+			else
+				goto invalid;
+			/* RHS */
+			if (!rs[i].dst)
+				; /* missing is ok; it is the same as empty */
+			else if (!*rs[i].dst)
+				; /* empty is ok; it means "do not store" */
+			else if (!check_refname_format(rs[i].dst, flags))
+				; /* valid looking ref is ok */
+			else
+				goto invalid;
+		} else {
+			/*
+			 * LHS
+			 * - empty is allowed; it means delete.
+			 * - when wildcarded, it must be a valid looking ref.
+			 * - otherwise, it must be an extended SHA-1, but
+			 *   there is no existing way to validate this.
+			 */
+			if (!*rs[i].src)
+				; /* empty is ok */
+			else if (is_glob) {
+				if (check_refname_format(rs[i].src, flags))
+					goto invalid;
+			}
+			else
+				; /* anything goes, for now */
+			/*
+			 * RHS
+			 * - missing is allowed, but LHS then must be a
+			 *   valid looking ref.
+			 * - empty is not allowed.
+			 * - otherwise it must be a valid looking ref.
+			 */
+			if (!rs[i].dst) {
+				if (check_refname_format(rs[i].src, flags))
+					goto invalid;
+			} else if (!*rs[i].dst) {
+				goto invalid;
+			} else {
+				if (check_refname_format(rs[i].dst, flags))
+					goto invalid;
+			}
+		}
+	}
+	return rs;
+
+ invalid:
+	if (verify) {
+		/*
+		 * nr_refspec must be greater than zero and i must be valid
+		 * since it is only possible to reach this point from within
+		 * the for loop above.
+		 */
+		free_refspec(i+1, rs);
+		return NULL;
+	}
+	die("Invalid refspec '%s'", refspec[i]);
+}
+
+int valid_fetch_refspec(const char *fetch_refspec_str)
+{
+	struct refspec *refspec;
+
+	refspec = parse_refspec_internal(1, &fetch_refspec_str, 1, 1);
+	free_refspec(1, refspec);
+	return !!refspec;
+}
+
+struct refspec *parse_fetch_refspec(int nr_refspec, const char **refspec)
+{
+	return parse_refspec_internal(nr_refspec, refspec, 1, 0);
+}
+
+struct refspec *parse_push_refspec(int nr_refspec, const char **refspec)
+{
+	return parse_refspec_internal(nr_refspec, refspec, 0, 0);
+}
+
+void free_refspec(int nr_refspec, struct refspec *refspec)
+{
+	int i;
+
+	if (!refspec)
+		return;
+
+	for (i = 0; i < nr_refspec; i++) {
+		free(refspec[i].src);
+		free(refspec[i].dst);
+	}
+	free(refspec);
+}