setup_git_directory: delay core.bare/core.worktree errors

If both core.bare and core.worktree are set, we complain
about the bogus config and die. Dying is good, because it
avoids commands running and doing damage in a potentially
incorrect setup. But dying _there_ is bad, because it means
that commands which do not even care about the work tree
cannot run. This can make repairing the situation harder:

  [setup]
  $ git config core.bare true
  $ git config core.worktree /some/path

  [OK, expected.]
  $ git status
  fatal: core.bare and core.worktree do not make sense

  [Hrm...]
  $ git config --unset core.worktree
  fatal: core.bare and core.worktree do not make sense

  [Nope...]
  $ git config --edit
  fatal: core.bare and core.worktree do not make sense

  [Gaaah.]
  $ git help config
  fatal: core.bare and core.worktree do not make sense

Instead, let's issue a warning about the bogus config when
we notice it (i.e., for all commands), but only die when the
command tries to use the work tree (by calling setup_work_tree).
So we now get:

  $ git status
  warning: core.bare and core.worktree do not make sense
  fatal: unable to set up work tree using invalid config

  $ git config --unset core.worktree
  warning: core.bare and core.worktree do not make sense

We have to update t1510 to accomodate this; it uses
symbolic-ref to check whether the configuration works or
not, but of course that command does not use the working
tree. Instead, we switch it to use `git status`, as it
requires a work-tree, does not need any special setup, and
is read-only (so a failure will not adversely affect further
tests).

In addition, we add a new test that checks the desired
behavior (i.e., that running "git config" with the bogus
config does in fact work).
Reported-by: NSZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

setup.c

@@ -4,6 +4,7 @@
 
 static int inside_git_dir = -1;
 static int inside_work_tree = -1;
+static int work_tree_config_is_bogus;
 
 /*
  * The input parameter must contain an absolute path, and it must already be
@@ -286,6 +287,10 @@ void setup_work_tree(void)
 
 	if (initialized)
 		return;
+
+	if (work_tree_config_is_bogus)
+		die("unable to set up work tree using invalid config");
+
 	work_tree = get_git_work_tree();
 	git_dir = get_git_dir();
 	if (!is_absolute_path(git_dir))
@@ -422,8 +427,11 @@ static const char *setup_explicit_git_dir(const char *gitdirenv,
 	if (work_tree_env)
 		set_git_work_tree(work_tree_env);
 	else if (is_bare_repository_cfg > 0) {
-		if (git_work_tree_cfg) /* #22.2, #30 */
-			die("core.bare and core.worktree do not make sense");
+		if (git_work_tree_cfg) {
+			/* #22.2, #30 */
+			warning("core.bare and core.worktree do not make sense");
+			work_tree_config_is_bogus = 1;
+		}
 
 		/* #18, #26 */
 		set_git_dir(gitdirenv);

t/t1510-repo-setup.sh

@@ -598,11 +598,20 @@ test_expect_success '#20b/c: core.worktree and core.bare conflict' '
 	mkdir -p 20b/.git/wt/sub &&
 	(
 		cd 20b/.git &&
-		test_must_fail git symbolic-ref HEAD >/dev/null
+		test_must_fail git status >/dev/null
 	) 2>message &&
 	grep "core.bare and core.worktree" message
 '
 
+test_expect_success '#20d: core.worktree and core.bare OK when working tree not needed' '
+	setup_repo 20d non-existent "" true &&
+	mkdir -p 20d/.git/wt/sub &&
+	(
+		cd 20d/.git &&
+		git config foo.bar value
+	)
+'
+
 # Case #21: core.worktree/GIT_WORK_TREE overrides core.bare' '
 test_expect_success '#21: setup, core.worktree warns before overriding core.bare' '
 	setup_repo 21 non-existent "" unset &&
@@ -611,7 +620,7 @@ test_expect_success '#21: setup, core.worktree warns before overriding core.bare
 		cd 21/.git &&
 		GIT_WORK_TREE="$here/21" &&
 		export GIT_WORK_TREE &&
-		git symbolic-ref HEAD >/dev/null
+		git status >/dev/null
 	) 2>message &&
 	! test -s message
 
@@ -700,13 +709,13 @@ test_expect_success '#22.2: core.worktree and core.bare conflict' '
 		cd 22/.git &&
 		GIT_DIR=. &&
 		export GIT_DIR &&
-		test_must_fail git symbolic-ref HEAD 2>result
+		test_must_fail git status 2>result
 	) &&
 	(
 		cd 22 &&
 		GIT_DIR=.git &&
 		export GIT_DIR &&
-		test_must_fail git symbolic-ref HEAD 2>result
+		test_must_fail git status 2>result
 	) &&
 	grep "core.bare and core.worktree" 22/.git/result &&
 	grep "core.bare and core.worktree" 22/result
@@ -752,9 +761,8 @@ test_expect_success '#28: core.worktree and core.bare conflict (gitfile case)' '
 	setup_repo 28 "$here/28" gitfile true &&
 	(
 		cd 28 &&
-		test_must_fail git symbolic-ref HEAD
+		test_must_fail git status
 	) 2>message &&
-	! grep "^warning:" message &&
 	grep "core.bare and core.worktree" message
 '
 
@@ -766,7 +774,7 @@ test_expect_success '#29: setup' '
 		cd 29 &&
 		GIT_WORK_TREE="$here/29" &&
 		export GIT_WORK_TREE &&
-		git symbolic-ref HEAD >/dev/null
+		git status
 	) 2>message &&
 	! test -s message
 '
@@ -777,7 +785,7 @@ test_expect_success '#30: core.worktree and core.bare conflict (gitfile version)
 	setup_repo 30 "$here/30" gitfile true &&
 	(
 		cd 30 &&
-		test_must_fail env GIT_DIR=.git git symbolic-ref HEAD 2>result
+		test_must_fail env GIT_DIR=.git git status 2>result
 	) &&
 	grep "core.bare and core.worktree" 30/result
 '