Re: [PATCH] format-patch: Update the `-3` example

On Sat, 21 Aug 2010, Ramkumar Ramachandra wrote:

Ramkumar Ramachandra writes:

quoted

Jakub Narebski writes:

quoted

Works for me:

  5031:[gitweb/split@git]# git format-patch -3
  0001-gitweb-Prepare-for-splitting-gitweb.txt
  0002-gitweb-Create-Gitweb-Git-module.txt

  5034:[gitweb/split@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'

or

B. Modify git-format-patch so that "git format-patch -<n>" would always
   generate <n> patches from specified commits, if there are that many.

But I think that option B.) it might be difficult, so perhaps A.) is 
"it". 
-- 
Jakub Narebski
Poland