odb: consistently use "dir" to refer to alternate's directory

The functions that add an alternate object directory to the object
database are somewhat inconsistent in how they call the paramater that
refers to the directory path: in our headers we refer to it as "dir",
whereas in the implementation we often call it "reference" or "entry".

Unify this and consistently call the parameter "dir". While at it,
refactor `link_alt_odb_entry()` to accept a C string instead of a
`struct strbuf` as parameter to clarify that we really only need the
path and nothing else.

Suggested-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

odb.c

@@ -140,7 +140,7 @@ static void read_info_alternates(struct object_database *odb,
 				 int depth);
 
 static int link_alt_odb_entry(struct object_database *odb,
-			      const struct strbuf *entry,
+			      const char *dir,
 			      const char *relative_base,
 			      int depth,
 			      const char *normalized_objdir)
@@ -151,11 +151,11 @@ static int link_alt_odb_entry(struct object_database *odb,
 	khiter_t pos;
 	int ret = -1;
 
-	if (!is_absolute_path(entry->buf) && relative_base) {
+	if (!is_absolute_path(dir) && relative_base) {
 		strbuf_realpath(&pathbuf, relative_base, 1);
 		strbuf_addch(&pathbuf, '/');
 	}
-	strbuf_addbuf(&pathbuf, entry);
+	strbuf_addstr(&pathbuf, dir);
 
 	if (!strbuf_realpath(&tmp, pathbuf.buf, 0)) {
 		error(_("unable to normalize alternate object path: %s"),
@@ -229,7 +229,7 @@ static void link_alt_odb_entries(struct object_database *odb, const char *alt,
 				 int sep, const char *relative_base, int depth)
 {
 	struct strbuf objdirbuf = STRBUF_INIT;
-	struct strbuf entry = STRBUF_INIT;
+	struct strbuf dir = STRBUF_INIT;
 
 	if (!alt || !*alt)
 		return;
@@ -243,13 +243,13 @@ static void link_alt_odb_entries(struct object_database *odb, const char *alt,
 	strbuf_realpath(&objdirbuf, odb->sources->path, 1);
 
 	while (*alt) {
-		alt = parse_alt_odb_entry(alt, sep, &entry);
-		if (!entry.len)
+		alt = parse_alt_odb_entry(alt, sep, &dir);
+		if (!dir.len)
 			continue;
-		link_alt_odb_entry(odb, &entry,
+		link_alt_odb_entry(odb, dir.buf,
 				   relative_base, depth, objdirbuf.buf);
 	}
-	strbuf_release(&entry);
+	strbuf_release(&dir);
 	strbuf_release(&objdirbuf);
 }
 
@@ -273,7 +273,7 @@ static void read_info_alternates(struct object_database *odb,
 }
 
 void odb_add_to_alternates_file(struct object_database *odb,
-				const char *reference)
+				const char *dir)
 {
 	struct lock_file lock = LOCK_INIT;
 	char *alts = repo_git_path(odb->repo, "objects/info/alternates");
@@ -290,7 +290,7 @@ void odb_add_to_alternates_file(struct object_database *odb,
 		struct strbuf line = STRBUF_INIT;
 
 		while (strbuf_getline(&line, in) != EOF) {
-			if (!strcmp(reference, line.buf)) {
+			if (!strcmp(dir, line.buf)) {
 				found = 1;
 				break;
 			}
@@ -306,27 +306,25 @@ void odb_add_to_alternates_file(struct object_database *odb,
 	if (found) {
 		rollback_lock_file(&lock);
 	} else {
-		fprintf_or_die(out, "%s\n", reference);
+		fprintf_or_die(out, "%s\n", dir);
 		if (commit_lock_file(&lock))
 			die_errno(_("unable to move new alternates file into place"));
 		if (odb->loaded_alternates)
-			link_alt_odb_entries(odb, reference,
-					     '\n', NULL, 0);
+			link_alt_odb_entries(odb, dir, '\n', NULL, 0);
 	}
 	free(alts);
 }
 
 void odb_add_to_alternates_memory(struct object_database *odb,
-				  const char *reference)
+				  const char *dir)
 {
 	/*
 	 * Make sure alternates are initialized, or else our entry may be
 	 * overwritten when they are.
 	 */
 	odb_prepare_alternates(odb);
 
-	link_alt_odb_entries(odb, reference,
-			     '\n', NULL, 0);
+	link_alt_odb_entries(odb, dir, '\n', NULL, 0);
 }
 
 struct odb_source *odb_set_temporary_primary_source(struct object_database *odb,