From: Simon Oosthoek <s.oosthoek@xs4all.nl>
Date: Wed, 26 Dec 2012 21:03:24 GMT
Subject: Re: [PATCH] make __git_ps1 accept a third parameter in pcmode
Message-ID: <20121226210324.GA20704@xs4all.nl>
In-Reply-To: <7vfw2so8q3.fsf@alter.siamese.dyndns.org>

* Junio C Hamano <gitster@pobox.com> [2012-12-26 12:32:20 -0800]:
> The point of the above two was that __git_ps1 does not have to set
> PS1 as long as the insn says user to use PROMPT_COMMAND that sets
> PS1 himself, exactly as illustrated above.  In other words, replace
> the last PS1=...  in the "prompt command" mode with an echo or
> something and make the user responsible for assigning it to PS1 in
> his PROMPT_COMMAND.
> 
> Or put it in another way, I was hoping that we can do without adding
> the prompt command mode---if there is no two modes, there is no need
> to switch between them.
> 
> But as I said, there probably is a reason why that approach does not
> work, that is why I said...
> 

The only reason to my knowledge is that bash's handling of zero-length strings, like terminal colour commands, is producing a PS1 that outputs less visible characters than bash thinks and thus bash makes mistakes when wrapping the commandline. The way to prevent that is to use \[ and \] around those and that doesn't seem to work from a string produced from command-substitution. (BTW, the colours come through just fine, just the \[ and \] don't)

Another approach could be to split up the functionality and have a few support functions to set various variables (corresponding with the gitstring features, like *%+ characters and colour hints). These variables could then be used by a custom PROMPT_COMMAND function or a command substitution function to produce a gitstring. I suppose that would mean a complete rewrite or very close to it ;-)

/Simon