Re: WARNING: Git merges are tricky. Rebasing is better?

[Kyle Meyer]

Leo Famulari writes:

> ------
> $ git show 276f40fdc349d2ad62582b23ea55e061b689cfc0:gnu/packages/gnome.scm | 
> grep "define-public epiphany" -A11
> (define-public epiphany
>   (package
>     (name "epiphany")
>     (version "41.2")
>     (source (origin
>               (method url-fetch)
>               (uri (string-append "mirror://gnome/sources/epiphany/"
>                                   (version-major version) "/"
>                                   "epiphany-" version ".tar.xz"))
>               (sha256
>                (base32
>                 "0r7m34xzz3shdfxf2abxb069izak3yv3ijlg29qy4pfmyawkilfs"))
> ------           ^
>                 *This is the hash of Epiphany 40.3, the old version!*
>
> Git's automatic merge conflict resolution algorithm did the wrong thing
> here. And Git does not show the reversion in `git log`, hiding it from
> review.
>
> My guess is that commit f7afefba0 ("gnu: epiphany: Fix build with
> libportal-0.5."), which happened on the master branch while the
> version-1.4.0 branch was forked off, made Git think that this line was
> more "up to date" on master than on version-1.4.0, causing it to select
> the old hash when faced with the conflict.

Fwiw I don't think Git automatically resolved that conflict:

  $ git checkout 276f40fdc349d2ad62582b23ea55e061b689cfc0^
  $ git merge 276f40fdc349d2ad62582b23ea55e061b689cfc0^2
  
  $ git status -- gnu/packages/gnome.scm
  HEAD detached at b2f6b6f6b9
  You have unmerged paths.
  
  Unmerged paths:
        both modified:   gnu/packages/gnome.scm
  
  no changes added to commit
  
  $ git diff -- gnu/packages/gnome.scm
  diff --cc gnu/packages/gnome.scm
  index d8d34c89ed,6c63b8bc59..0000000000
  --- a/gnu/packages/gnome.scm
  +++ b/gnu/packages/gnome.scm
  @@@ -6433,13 -6415,10 +6421,12 @@@ supports playlists, song ratings, and a
                                    name "-" version ".tar.xz"))
                (sha256
                 (base32
   -              "0ddjwcd77nw0rxb5x5bz5hd671m8gya9827p8rsnb58x103kpai8"))))
   +              "0ddjwcd77nw0rxb5x5bz5hd671m8gya9827p8rsnb58x103kpai8"))
   +            ;; XXX: Remove when upgrading to 42.0
   +            (patches (search-patches "eog-update-libportal-usage.patch"))))
       (build-system meson-build-system)
       (arguments
  -     `(#:meson ,meson-0.59         ;positional arguments error with meson 
0.60
  -       #:configure-flags
  +     `(#:configure-flags
          ;; Otherwise, the RUNPATH will lack the final 'eog' path component.
          (list (string-append "-Dc_link_args=-Wl,-rpath="
                               (assoc-ref %outputs "out") "/lib/eog"))
  @@@ -6798,9 -6776,8 +6784,17 @@@ a secret password store, an adblocker, 
                                      "epiphany-" version ".tar.xz"))
                  (sha256
                   (base32
  ++<<<<<<< HEAD
   +                "0r7m34xzz3shdfxf2abxb069izak3yv3ijlg29qy4pfmyawkilfs"))
   +              (patches
   +               (search-patches "epiphany-update-libportal-usage.patch"))))
  ++||||||| d91de53caa
  ++                "0r7m34xzz3shdfxf2abxb069izak3yv3ijlg29qy4pfmyawkilfs"))))
  ++
  ++=======
  +                 "0k7b22zq3z1kllzqxgwsvwb1lp0j6rjb3k1hvhna3i573wc4mpji"))))
  + 
  ++>>>>>>> 276f40fdc349d2ad62582b23ea55e061b689cfc0^2
        (build-system meson-build-system)
        (arguments
         `(#:glib-or-gtk? #t