setup: don't perform lazy initialization of repository state

Under some circumstances (bogus GIT_DIR value or the discovered gitdir
is '.git') 'setup_git_directory()' won't initialize key repository
state.  This leads to inconsistent state after running the setup code.
To account for this inconsistent state, lazy initialization is done once
a caller asks for the repository's gitdir or some other piece of
repository state.  This is confusing and can be error prone.

Instead let's tighten the expected outcome of 'setup_git_directory()'
and ensure that it initializes repository state in all cases that would
have been handled by lazy initialization.

This also lets us drop the requirement to have 'have_git_dir()' check if
the environment variable GIT_DIR was set as that will be handled by the
end of the setup code.

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

setup.c

@@ -1091,6 +1091,20 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	startup_info->have_repository = !nongit_ok || !*nongit_ok;
 	startup_info->prefix = prefix;
 
+	/*
+	 * Not all paths through the setup code will call 'set_git_dir()' (which
+	 * directly sets up the environment) so in order to guarantee that the
+	 * environment is in a consistent state after setup, explicitly setup
+	 * the environment if we have a repository.
+	 *
+	 * NEEDSWORK: currently we allow bogus GIT_DIR values to be set in some
+	 * code paths so we also need to explicitly setup the environment if
+	 * the user has set GIT_DIR.  It may be beneficial to disallow bogus
+	 * GIT_DIR values at some point in the future.
+	 */
+	if (startup_info->have_repository || getenv(GIT_DIR_ENVIRONMENT))
+		setup_git_env();
+
 	strbuf_release(&dir);
 	strbuf_release(&gitdir);