The tab completion for darcs2 looks broken because the current line gets
overwritten.

This could be solved by adding --quiet in the right place in
tools/darcs_completion, assuming all commands take a "--quiet" option. 

However, as you can see by testing on the darcs repo itself, the "--quiet"
option is not currently quiet when used with the "add" command. It still outputs
a progress report, which looks rather broken it is being used as the backend to
the tab completion trick:

 cd tools/
 darcs add --quiet --list-options

Hi Mark,

I'm pushing a patch that disables progress reporting when --list-options is
specified.  I think this is the nicest approach.  I'll close this for now,
although I'd appreciate confirmation that this works.  And even better if you
can figure out how to write a test.

David

After trying this, I got an unexpected result:

cd tests/
darcs add <tab> 

It returned over 1,000 possible completions, including some like these:

.darcs/cache
.darcs/cache/pristine.hashed
.darcs/cache/pristine.hashed/c2c9ec37603f8960774e4ff0deff2a28ef5f96ac

It seems like something changed about the --list-options command works.

This is resolved now, I just didn't understand the correct result that was being
returned earlier. I was seeing files that had been created in the tests
directory, including ".darcs", which had been created but not cleaned up. It was
correct for tab-completion to offer to add these, if surprising. 

As an edge case, that darcs recursively looked in all the directories could be a
performance problem. Perhaps it should act more like the shell and only complete
one directory level at a time, rather than doing a slower recursive search up
front. That's a different bug report if someone wants to to re-open it..