Ramkumar Ramachandra | 21 Aug 18:49 2010
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Re: [PATCH] format-patch: Update the `-3` example

Hi Jakub,

Jakub Narebski writes:
> On Sat, 21 Aug 2010, Ramkumar Ramachandra wrote:
> > Ramkumar Ramachandra writes:
> > > Jakub Narebski writes:
> > > > Works for me:
> > > > 
> > > >   5031:[gitweb/split <at> git]# git format-patch -3
> > > >   0001-gitweb-Prepare-for-splitting-gitweb.txt
> > > >   0002-gitweb-Create-Gitweb-Git-module.txt
> > > > 
> > > >   5034:[gitweb/split <at> git]# git version
> > > >   git version 1.7.2.1
> > > > 
> > > > 
> > > > The -3 is git-log option:
> > > > 
> > > >   -<n>   Limits the number of commits to show.
> > > > 
> > > > and also git-format-patch option:
> > > > 
> > > >   -<n>   Limits the number of patches to prepare.
> > > 
> > > Hm, doesn't work on the `pu` Git, but works on `master` -- I'm
> > > currently bisecting to find the problem. `git log -3` works
> > > though.
> > 
> > :facepalm:
> > 
> > Scratch out what I just said -- I just realized that `git format-patch
> > HEAD~3` handles merge commits, but `git format-patch -3` does
> > not. `git format-patch -3 HEAD~3` is even more confusing- should we
> > even advertise the `-<n>` option in format-patch?
> 
> It looks like there is a conceptual bug in how git-format-patch works, 
> namely that '-<n>' is passed to rev-list / log generating machinery, 
> and it limits number of *commits* to consider; if some of those commits 
> are merge commits, which cannot be represented as patches, the number 
> of patches it generates is less than specified <n> (as you can see in 
> the example I have provided, where <n> == 3, and git-format-patch 
> generated 2 patches, not 3).  In extreme case (like 'pu') it can 
> generate no patch.
> 
> I am not sure what the solution should be.  We could either:
> 
> A. Update git-format-patch documentation to say 'commits' instead of
>    'patches', and perhaps also be loud about commits we are skipping,
>    so that my example would look e.g. like this:
> 
>      $ git format-patch -3
>      0001-gitweb-Prepare-for-splitting-gitweb.txt
>      0002-gitweb-Create-Gitweb-Git-module.txt
>      Skipping merge commit: Merge branch 'maint'

Thanks for the awesome explanation! A is definitely the way to go-
I'll start writing a patch immediately.

-- Ram

Gmane