doc txt & -h consistency: word-wrap

Change the documentation and -h output for those built-in commands
where both the -h output and *.txt were lacking in word-wrapping.

There are many more built-ins that could use this treatment, this
change is narrowed to those where this whitespace change is needed to
make the -h and *.txt consistent in the end.

In the case of "Documentation/git-hash-object.txt" and
"builtin/hash-object.c" this is not a "doc txt & -h consistency"
change, as we're changing both versions, doing so here makes a
subsequent change smaller.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit-tree.c

@@ -15,8 +15,8 @@
 #include "parse-options.h"
 
 static const char * const commit_tree_usage[] = {
-	N_("git commit-tree [(-p <parent>)...] [-S[<keyid>]] [(-m <message>)...] "
-		"[(-F <file>)...] <tree>"),
+	N_("git commit-tree [(-p <parent>)...] [-S[<keyid>]] [(-m <message>)...]\n"
+	   "                [(-F <file>)...] <tree>"),
 	NULL
 };