check-docs: get documented command list from Makefile

The current code tries to get a list of documented commands
by doing "ls Documentation/git*txt" and culling a bunch of
special cases from the result. Looking for "git-*.txt" would
be more accurate, but would miss a few commands like
"gitweb" and "gitk".

Fortunately, Documentation/Makefile already knows what this
list is, so we can just ask it. Annoyingly, we still have to
post-process its output a little, since make will print
extra cruft like "GIT-VERSION-FILE is up to date" to stdout.

Now that our list is accurate, we can remove all of the ugly
special-cases.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/Makefile

@@ -344,4 +344,7 @@ require-htmlrepo::
 quick-install-html: require-htmlrepo
 	'$(SHELL_PATH_SQ)' ./install-doc-quick.sh $(HTML_REPO) $(DESTDIR)$(htmldir)
 
+print-man1:
+	@for i in $(MAN1_TXT); do echo $$i; done
+
 .PHONY: FORCE

Makefile

@@ -2832,34 +2832,12 @@ check-docs::
 		sed -e '/^#/d' \
 		    -e 's/[ 	].*//' \
 		    -e 's/^/listed /' command-list.txt; \
-		ls -1 Documentation/git*txt | \
+		$(MAKE) -C Documentation print-man1 | \
+		grep '\.txt$$' | \
 		sed -e 's|Documentation/|documented |' \
 		    -e 's/\.txt//'; \
 	) | while read how cmd; \
 	do \
-		case "$$how,$$cmd" in \
-		documented,gitattributes | \
-		documented,gitignore | \
-		documented,gitmodules | \
-		documented,gitcli | \
-		documented,git-tools | \
-		documented,gitcore-tutorial | \
-		documented,gitcvs-migration | \
-		documented,gitdiffcore | \
-		documented,gitglossary | \
-		documented,githooks | \
-		documented,gitrepository-layout | \
-		documented,gitrevisions | \
-		documented,gittutorial | \
-		documented,gittutorial-2 | \
-		documented,git-bisect-lk2009 | \
-		documented,git-remote-helpers | \
-		documented,gitworkflows | \
-		documented,gitcredentials | \
-		documented,gitnamespaces | \
-		documented,gitweb.conf | \
-		sentinel,not,matching,is,ok ) continue ;; \
-		esac; \
 		case " $(ALL_COMMANDS) " in \
 		*" $$cmd "*)	;; \
 		*) echo "removed but $$how: $$cmd" ;; \