Re: [PATCH] Improve vcs_info example for ahead/behind git commits

[Tim Lee <progscriptclone@gmail.com>]

> > > > diff --git a/Misc/vcs_info-examples b/Misc/vcs_info-examples
> > > > index 94b8a7b5e..36d4d3bf8 100644
> > > > --- a/Misc/vcs_info-examples
> > > > +++ b/Misc/vcs_info-examples
> > > > @@ -179,14 +179,18 @@ function +vi-git-st() {
> > > >      local ahead behind
> > > >      local -a gitstatus
> > > > 
> > > > -    # for git prior to 1.7
> > > > +    # for git prior to 1.7.0
> > > >      # ahead=$(git rev-list origin/${hook_com[branch]}..HEAD | wc -l)
> > > > -    ahead=$(git rev-list ${hook_com[branch]}@{upstream}..HEAD 2>/dev/null | wc -l)
> > > > +    # for git 1.7.0 and 1.7.1
> > > > +    # ahead=$(git rev-list @{upstream}..HEAD 2>/dev/null | wc -l)
> > > > +    ahead=$(git rev-list --count @{upstream}..HEAD 2>/dev/null)
> > > >      (( $ahead )) && gitstatus+=( "+${ahead}" )
> > > 
> > > The version of this function in my zshrc starts like this:
> > > .
> > >     git rev-parse @{upstream} >/dev/null 2>&1 || return 0
> > >     local -a x=( $(git rev-list --left-right --count HEAD...@{upstream} ) )
> > 
> > The snippet below displays N/M. How would you make it display +N/-M
> > instead?
> 
> Change the last line to hook_com[misc]="+${x[1]} -${x[2]}".

But hook_com[misc]="+${x[1]} -${x[2]}" would display a '+0' and/or '-0'
when the local git branch is not ahead-of or behind the remote branch.

The existing example does not display '+0' or '-0'.

> >     git rev-parse @{upstream} >/dev/null 2>&1 || return 0
> >     local -a x=( $(git rev-list --left-right --count HEAD...@{upstream} ) )
> >     hook_com[misc]="${(j:/:)x}"
> > 
> > > The first line is to handle a detached HEAD, I think, and should
> > > presumably be added?
> > 
> > Why not do this instead:
> > 
> >     local -a x=( $(git rev-list --left-right --count HEAD...@{upstream} 2>/dev/null ) )
> 
> You mean, why not discard stderr?  Out of general principles ("Errors
> shouldn't be silenced"), plus the fact that I've never had that line
> generate an error that needed to be silenced — not with the «git
> rev-parse … || return» right above it.
> 
> Or do you mean that line instead of the git-rev-parse(1) call too?

Yes, I mean: instead of this:

     git rev-parse @{upstream} >/dev/null 2>&1 || return 0
     local -a x=( $(git rev-list --left-right --count HEAD...@{upstream} ) )

Replace both of the lines above with this:

     local -a x=( $(git rev-list --left-right --count HEAD...@{upstream} 2>/dev/null ) )

> First, that would run the rest of the function even though $x might be
> an empty array rather than a two-element one.  Two, suppose there is an
> error after resolving «@{upstream}» to a commit but before rev-list
> finishes (for instance, an error while walking the commits history).
> With an explicit git-rev-parse(1) call that error would be reported, but
> if the rev-parse and the history walking are lumped into one step any
> failure from which is treated the same way, history walking failures
> would be masked — even though they're probably interesting.
> 
> > ---
> > Note: when replying to my email, please ensure that my email address is
> > included in the 'To:' field, since I am not subscribed to the mailing
> > list.
> 
> Ack, but for future reference, the customary signature delimiter is "-- "
> (ASCII 0x2D 0x2D 0x20).  Many MUAs syntax-highlight that, for example.

Thank you for all this information. I've learned so much today. :-)