rename default branch from 'master' to 'main' in refs and test scripts

Author: huangsen365

refs.c

@@ -653,7 +653,7 @@ char *repo_default_branch_name(struct repository *r, int quiet)
 		die(_("could not retrieve `%s`"), config_display_key);
 
 	if (!ret) {
-		ret = xstrdup("master");
+		ret = xstrdup("main");
 		if (!quiet)
 			advise_if_enabled(ADVICE_DEFAULT_BRANCH_NAME,
 					  _(default_branch_name_advice), ret);

remote.c

@@ -2379,7 +2379,7 @@ struct ref *guess_remote_head(const struct ref *head,
 			return copy_ref(r);
 
 		/* Fall back to the hard-coded historical default */
-		r = find_ref_by_name(refs, "refs/heads/master");
+		r = find_ref_by_name(refs, "refs/heads/main");
 		if (r && oideq(&r->old_oid, &head->old_oid))
 			return copy_ref(r);
 	}

t/test-lib.sh

@@ -129,7 +129,7 @@ fi
 
 # Explicitly set the default branch name for testing, to avoid the
 # transitory "git init" warning under --verbose.
-: ${GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME:=master}
+: ${GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME:=main}
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
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