refs: unify parse_worktree_ref() and ref_type()

The logic to handle worktree refs (worktrees/NAME/REF and
main-worktree/REF) existed in two places:

* ref_type() in refs.c

* parse_worktree_ref() in worktree.c

Collapse this logic together in one function parse_worktree_ref():
this avoids having to cross-check the result of parse_worktree_ref()
and ref_type().

Introduce enum ref_worktree_type, which is slightly different from
enum ref_type. The latter is a misleading name (one would think that
'ref_type' would have the symref option).

Instead, enum ref_worktree_type only makes explicit how a refname
relates to a worktree. From this point of view, HEAD and
refs/bisect/abc are the same: they specify the current worktree
implicitly.

The files-backend must avoid packing refs/bisect/* and friends into
packed-refs, so expose is_per_worktree_ref() separately.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/reflog.c

@@ -67,7 +67,8 @@ static int collect_reflog(const char *ref, const struct object_id *oid UNUSED,
 	 * Avoid collecting the same shared ref multiple times because
 	 * they are available via all worktrees.
 	 */
-	if (!worktree->is_current && ref_type(ref) == REF_TYPE_NORMAL)
+	if (!worktree->is_current &&
+	    parse_worktree_ref(ref, NULL, NULL, NULL) == REF_WORKTREE_SHARED)
 		return 0;
 
 	strbuf_worktree_ref(worktree, &newref, ref);

reflog.c

@@ -312,16 +312,9 @@ static int push_tip_to_list(const char *refname UNUSED,
 
 static int is_head(const char *refname)
 {
-	switch (ref_type(refname)) {
-	case REF_TYPE_OTHER_PSEUDOREF:
-	case REF_TYPE_MAIN_PSEUDOREF:
-		if (parse_worktree_ref(refname, NULL, NULL, &refname))
-			BUG("not a worktree ref: %s", refname);
-		break;
-	default:
-		break;
-	}
-	return !strcmp(refname, "HEAD");
+	const char *stripped_refname;
+	parse_worktree_ref(refname, NULL, NULL, &stripped_refname);
+	return !strcmp(stripped_refname, "HEAD");
 }
 
 void reflog_expiry_prepare(const char *refname,

refs.c

@@ -811,7 +811,7 @@ int dwim_log(const char *str, int len, struct object_id *oid, char **log)
 	return repo_dwim_log(the_repository, str, len, oid, log);
 }
 
-static int is_per_worktree_ref(const char *refname)
+int is_per_worktree_ref(const char *refname)
 {
 	return starts_with(refname, "refs/worktree/") ||
 	       starts_with(refname, "refs/bisect/") ||
@@ -827,37 +827,63 @@ static int is_pseudoref_syntax(const char *refname)
 			return 0;
 	}
 
+	/*
+	 * HEAD is not a pseudoref, but it certainly uses the
+	 * pseudoref syntax.
+	 */
 	return 1;
 }
 
-static int is_main_pseudoref_syntax(const char *refname)
-{
-	return skip_prefix(refname, "main-worktree/", &refname) &&
-		*refname &&
-		is_pseudoref_syntax(refname);
+static int is_current_worktree_ref(const char *ref) {
+	return is_pseudoref_syntax(ref) || is_per_worktree_ref(ref);
 }
 
-static int is_other_pseudoref_syntax(const char *refname)
+enum ref_worktree_type parse_worktree_ref(const char *maybe_worktree_ref,
+					  const char **worktree_name, int *worktree_name_length,
+					  const char **bare_refname)
 {
-	if (!skip_prefix(refname, "worktrees/", &refname))
-		return 0;
-	refname = strchr(refname, '/');
-	if (!refname || !refname[1])
-		return 0;
-	return is_pseudoref_syntax(refname + 1);
-}
+	const char *name_dummy;
+	int name_length_dummy;
+	const char *ref_dummy;
 
-enum ref_type ref_type(const char *refname)
-{
-	if (is_per_worktree_ref(refname))
-		return REF_TYPE_PER_WORKTREE;
-	if (is_pseudoref_syntax(refname))
-		return REF_TYPE_PSEUDOREF;
-	if (is_main_pseudoref_syntax(refname))
-		return REF_TYPE_MAIN_PSEUDOREF;
-	if (is_other_pseudoref_syntax(refname))
-		return REF_TYPE_OTHER_PSEUDOREF;
-	return REF_TYPE_NORMAL;
+	if (!worktree_name)
+		worktree_name = &name_dummy;
+	if (!worktree_name_length)
+		worktree_name_length = &name_length_dummy;
+	if (!bare_refname)
+		bare_refname = &ref_dummy;
+
+	if (skip_prefix(maybe_worktree_ref, "worktrees/", bare_refname)) {
+		const char *slash = strchr(*bare_refname, '/');
+
+		*worktree_name = *bare_refname;
+		if (!slash) {
+			*worktree_name_length = strlen(*worktree_name);
+
+			/* This is an error condition, and the caller tell because the bare_refname is "" */
+			*bare_refname = *worktree_name + *worktree_name_length;
+			return REF_WORKTREE_OTHER;
+		}
+
+		*worktree_name_length = slash - *bare_refname;
+		*bare_refname = slash + 1;
+
+		if (is_current_worktree_ref(*bare_refname))
+			return REF_WORKTREE_OTHER;
+	}
+
+	*worktree_name = NULL;
+	*worktree_name_length = 0;
+
+	if (skip_prefix(maybe_worktree_ref, "main-worktree/", bare_refname)
+	    && is_current_worktree_ref(*bare_refname))
+		return REF_WORKTREE_MAIN;
+
+	*bare_refname = maybe_worktree_ref;
+	if (is_current_worktree_ref(maybe_worktree_ref))
+		return REF_WORKTREE_CURRENT;
+
+	return REF_WORKTREE_SHARED;
 }
 
 long get_files_ref_lock_timeout_ms(void)

refs.h

@@ -820,15 +820,34 @@ int parse_hide_refs_config(const char *var, const char *value, const char *);
  */
 int ref_is_hidden(const char *, const char *);
 
-enum ref_type {
-	REF_TYPE_PER_WORKTREE,	  /* refs inside refs/ but not shared       */
-	REF_TYPE_PSEUDOREF,	  /* refs outside refs/ in current worktree */
-	REF_TYPE_MAIN_PSEUDOREF,  /* pseudo refs from the main worktree     */
-	REF_TYPE_OTHER_PSEUDOREF, /* pseudo refs from other worktrees       */
-	REF_TYPE_NORMAL,	  /* normal/shared refs inside refs/        */
+/* Is this a per-worktree ref living in the refs/ namespace? */
+int is_per_worktree_ref(const char *refname);
+
+/* Describes how a refname relates to worktrees */
+enum ref_worktree_type {
+	REF_WORKTREE_CURRENT, /* implicitly per worktree, eg. HEAD or
+				 refs/bisect/SOMETHING */
+	REF_WORKTREE_MAIN, /* explicitly in main worktree, eg.
+			      main-worktree/HEAD */
+	REF_WORKTREE_OTHER, /* explicitly in named worktree, eg.
+			       worktrees/bla/HEAD */
+	REF_WORKTREE_SHARED, /* the default, eg. refs/heads/main */
 };
 
-enum ref_type ref_type(const char *refname);
+/*
+ * Parse a `maybe_worktree_ref` as a ref that possibly refers to a worktree ref
+ * (ie. either REFNAME, main-worktree/REFNAME or worktree/WORKTREE/REFNAME). It
+ * returns what kind of ref was found, and in case of REF_WORKTREE_OTHER, the
+ * worktree name is returned in `worktree_name` (pointing into
+ * `maybe_worktree_ref`) and `worktree_name_length`. The bare refname (the
+ * refname stripped of prefixes) is returned in `bare_refname`. The
+ * `worktree_name`, `worktree_name_length` and `bare_refname` arguments may be
+ * NULL.
+ */
+enum ref_worktree_type parse_worktree_ref(const char *maybe_worktree_ref,
+					  const char **worktree_name,
+					  int *worktree_name_length,
+					  const char **bare_refname);
 
 enum expire_reflog_flags {
 	EXPIRE_REFLOGS_DRY_RUN = 1 << 0,

refs/files-backend.c

@@ -138,44 +138,30 @@ static struct files_ref_store *files_downcast(struct ref_store *ref_store,
 	return refs;
 }
 
-static void files_reflog_path_other_worktrees(struct files_ref_store *refs,
-					      struct strbuf *sb,
-					      const char *refname)
-{
-	const char *real_ref;
-	const char *worktree_name;
-	int length;
-
-	if (parse_worktree_ref(refname, &worktree_name, &length, &real_ref))
-		BUG("refname %s is not a other-worktree ref", refname);
-
-	if (worktree_name)
-		strbuf_addf(sb, "%s/worktrees/%.*s/logs/%s", refs->gitcommondir,
-			    length, worktree_name, real_ref);
-	else
-		strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir,
-			    real_ref);
-}
-
 static void files_reflog_path(struct files_ref_store *refs,
 			      struct strbuf *sb,
 			      const char *refname)
 {
-	switch (ref_type(refname)) {
-	case REF_TYPE_PER_WORKTREE:
-	case REF_TYPE_PSEUDOREF:
+	const char *bare_refname;
+	const char *wtname;
+	int wtname_len;
+	enum ref_worktree_type wt_type = parse_worktree_ref(
+		refname, &wtname, &wtname_len, &bare_refname);
+
+	switch (wt_type) {
+	case REF_WORKTREE_CURRENT:
 		strbuf_addf(sb, "%s/logs/%s", refs->base.gitdir, refname);
 		break;
-	case REF_TYPE_OTHER_PSEUDOREF:
-	case REF_TYPE_MAIN_PSEUDOREF:
-		files_reflog_path_other_worktrees(refs, sb, refname);
+	case REF_WORKTREE_SHARED:
+	case REF_WORKTREE_MAIN:
+		strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, bare_refname);
 		break;
-	case REF_TYPE_NORMAL:
-		strbuf_addf(sb, "%s/logs/%s", refs->gitcommondir, refname);
+	case REF_WORKTREE_OTHER:
+		strbuf_addf(sb, "%s/worktrees/%.*s/logs/%s", refs->gitcommondir,
+			    wtname_len, wtname, bare_refname);
 		break;
 	default:
-		BUG("unknown ref type %d of ref %s",
-		    ref_type(refname), refname);
+		BUG("unknown ref type %d of ref %s", wt_type, refname);
 	}
 }
 
@@ -183,22 +169,25 @@ static void files_ref_path(struct files_ref_store *refs,
 			   struct strbuf *sb,
 			   const char *refname)
 {
-	switch (ref_type(refname)) {
-	case REF_TYPE_PER_WORKTREE:
-	case REF_TYPE_PSEUDOREF:
+	const char *bare_refname;
+	const char *wtname;
+	int wtname_len;
+	enum ref_worktree_type wt_type = parse_worktree_ref(
+		refname, &wtname, &wtname_len, &bare_refname);
+	switch (wt_type) {
+	case REF_WORKTREE_CURRENT:
 		strbuf_addf(sb, "%s/%s", refs->base.gitdir, refname);
 		break;
-	case REF_TYPE_MAIN_PSEUDOREF:
-		if (!skip_prefix(refname, "main-worktree/", &refname))
-			BUG("ref %s is not a main pseudoref", refname);
-		/* fallthrough */
-	case REF_TYPE_OTHER_PSEUDOREF:
-	case REF_TYPE_NORMAL:
-		strbuf_addf(sb, "%s/%s", refs->gitcommondir, refname);
+	case REF_WORKTREE_OTHER:
+		strbuf_addf(sb, "%s/worktrees/%.*s/%s", refs->gitcommondir,
+			    wtname_len, wtname, bare_refname);
+		break;
+	case REF_WORKTREE_SHARED:
+	case REF_WORKTREE_MAIN:
+		strbuf_addf(sb, "%s/%s", refs->gitcommondir, bare_refname);
 		break;
 	default:
-		BUG("unknown ref type %d of ref %s",
-		    ref_type(refname), refname);
+		BUG("unknown ref type %d of ref %s", wt_type, refname);
 	}
 }
 
@@ -771,7 +760,8 @@ static int files_ref_iterator_advance(struct ref_iterator *ref_iterator)
 
 	while ((ok = ref_iterator_advance(iter->iter0)) == ITER_OK) {
 		if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
-		    ref_type(iter->iter0->refname) != REF_TYPE_PER_WORKTREE)
+		    parse_worktree_ref(iter->iter0->refname, NULL, NULL,
+				       NULL) != REF_WORKTREE_CURRENT)
 			continue;
 
 		if ((iter->flags & DO_FOR_EACH_OMIT_DANGLING_SYMREFS) &&
@@ -1178,7 +1168,8 @@ static int should_pack_ref(const char *refname,
 			   unsigned int pack_flags)
 {
 	/* Do not pack per-worktree refs: */
-	if (ref_type(refname) != REF_TYPE_NORMAL)
+	if (parse_worktree_ref(refname, NULL, NULL, NULL) !=
+	    REF_WORKTREE_SHARED)
 		return 0;
 
 	/* Do not pack non-tags unless PACK_REFS_ALL is set: */
@@ -2267,7 +2258,8 @@ static enum iterator_selection reflog_iterator_select(
 		 */
 		return ITER_SELECT_0;
 	} else if (iter_common) {
-		if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
+		if (parse_worktree_ref(iter_common->refname, NULL, NULL,
+				       NULL) == REF_WORKTREE_SHARED)
 			return ITER_SELECT_1;
 
 		/*

refs/packed-backend.c

@@ -862,7 +862,7 @@ static int packed_ref_iterator_advance(struct ref_iterator *ref_iterator)
 
 	while ((ok = next_record(iter)) == ITER_OK) {
 		if (iter->flags & DO_FOR_EACH_PER_WORKTREE_ONLY &&
-		    ref_type(iter->base.refname) != REF_TYPE_PER_WORKTREE)
+		    !is_per_worktree_ref(iter->base.refname))
 			continue;
 
 		if (!(iter->flags & DO_FOR_EACH_INCLUDE_BROKEN) &&

worktree.c

@@ -489,62 +489,17 @@ int submodule_uses_worktrees(const char *path)
 	return ret;
 }
 
-int parse_worktree_ref(const char *worktree_ref, const char **name,
-		       int *name_length, const char **ref)
-{
-	if (skip_prefix(worktree_ref, "main-worktree/", &worktree_ref)) {
-		if (!*worktree_ref)
-			return -1;
-		if (name)
-			*name = NULL;
-		if (name_length)
-			*name_length = 0;
-		if (ref)
-			*ref = worktree_ref;
-		return 0;
-	}
-	if (skip_prefix(worktree_ref, "worktrees/", &worktree_ref)) {
-		const char *slash = strchr(worktree_ref, '/');
-
-		if (!slash || slash == worktree_ref || !slash[1])
-			return -1;
-		if (name)
-			*name = worktree_ref;
-		if (name_length)
-			*name_length = slash - worktree_ref;
-		if (ref)
-			*ref = slash + 1;
-		return 0;
-	}
-	return -1;
-}
-
 void strbuf_worktree_ref(const struct worktree *wt,
 			 struct strbuf *sb,
 			 const char *refname)
 {
-	switch (ref_type(refname)) {
-	case REF_TYPE_PSEUDOREF:
-	case REF_TYPE_PER_WORKTREE:
-		if (wt && !wt->is_current) {
-			if (is_main_worktree(wt))
-				strbuf_addstr(sb, "main-worktree/");
-			else
-				strbuf_addf(sb, "worktrees/%s/", wt->id);
-		}
-		break;
-
-	case REF_TYPE_MAIN_PSEUDOREF:
-	case REF_TYPE_OTHER_PSEUDOREF:
-		break;
-
-	case REF_TYPE_NORMAL:
-		/*
-		 * For shared refs, don't prefix worktrees/ or
-		 * main-worktree/. It's not necessary and
-		 * files-backend.c can't handle it anyway.
-		 */
-		break;
+	if (parse_worktree_ref(refname, NULL, NULL, NULL) ==
+		    REF_WORKTREE_CURRENT &&
+	    wt && !wt->is_current) {
+		if (is_main_worktree(wt))
+			strbuf_addstr(sb, "main-worktree/");
+		else
+			strbuf_addf(sb, "worktrees/%s/", wt->id);
 	}
 	strbuf_addstr(sb, refname);
 }

worktree.h

@@ -166,16 +166,6 @@ const char *worktree_git_path(const struct worktree *wt,
 			      const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
 
-/*
- * Parse a worktree ref (i.e. with prefix main-worktree/ or
- * worktrees/) and return the position of the worktree's name and
- * length (or NULL and zero if it's main worktree), and ref.
- *
- * All name, name_length and ref arguments could be NULL.
- */
-int parse_worktree_ref(const char *worktree_ref, const char **name,
-		       int *name_length, const char **ref);
-
 /*
  * Return a refname suitable for access from the current ref store.
  */