doc txt & -h consistency: fix mismatching labels

Fix various inconsistencies between command SYNOPSIS and the
corresponding -h output where our translatable labels didn't match
up.

In some cases we need to adjust the prose that follows the SYNOPSIS
accordingly, as it refers back to the changed label.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
index c21cfd5..0a68935 100644
--- a/builtin/commit-graph.c
+++ b/builtin/commit-graph.c
@@ -10,10 +10,10 @@
 #include "tag.h"
 
 #define BUILTIN_COMMIT_GRAPH_VERIFY_USAGE \
-	N_("git commit-graph verify [--object-dir <objdir>] [--shallow] [--[no-]progress]")
+	N_("git commit-graph verify [--object-dir <dir>] [--shallow] [--[no-]progress]")
 
 #define BUILTIN_COMMIT_GRAPH_WRITE_USAGE \
-	N_("git commit-graph write [--object-dir <objdir>] [--append]\n" \
+	N_("git commit-graph write [--object-dir <dir>] [--append]\n" \
 	   "                       [--split[=<strategy>]] [--reachable | --stdin-packs | --stdin-commits]\n" \
 	   "                       [--changed-paths] [--[no-]max-new-filters <n>] [--[no-]progress]\n" \
 	   "                       <split options>")