check-docs: really look at the documented commands again

As part of the `check-docs` target, we verify that commands that are documented are actually in the current list of commands to be built. However, this logic broke in 5fafce0b78 (check-docs: get documented command list from Makefile, 2012-08-08), when we tried to make the logic safer by not looking at the files in the worktree, but at the list of files to be generated in `Documentation/Makefile`. While this was the right thing to do, it failed to accommodate for the fact that `make -C Documentation/ print-man1`, unlike `ls Documentation/*.txt`, would *not* print lines starting with the prefix `Documentation/`. At long last, let's fix this. Note: This went undetected due to a funny side effect of the `ALL_PROGRAMS` variable starting with a space. That space, together with the extra space we inserted before `$(ALL_PROGRAMS)` in the case " $(ALL_PROGRAMS)" in *" $$cmd ") [...] construct, is responsible that this case arm is used when `cmd` is empty (which was clearly not intended to be the case). Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>