Re: Can someone explain this git-blame/git-rev behavior to me?

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 16, 2007, 23:13 UTC
Message-ID: <7v7ip02b81.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <86sl7oaasx.fsf@lola.quinscape.zz>

David Kastrup <dak@gnu.org> writes:

Show 6 quoted lines

> git-rev-list HEAD --not tags/v1.4.2-rc1~88 --parents contrib/emacs/vc-git.el|tail -1|git-name-rev --stdin
>
> d87b90e47f7430455385edcf8506288b9a73d3b5 (tags/v1.4.2-rc1~87) b5dd9d2027c1bd5758033c7baf6d087752b0263d (tags/v1.4.2-rc1~88) 280242d1cc1fe2847f649d2f16b273e168fcbc48 (tags/v1.4.2-rc1~92)
>
> So we have tags/v1.4.2-rc1~87 listed as successor again, so I get into
> a loop of blame.

Without the final name-rev, it reads:

d87b90e4... b5dd9d20... 280242d1...

Without the --parent option, you get only d87b90e4...; the option tells the command to additionally give you the (virtual) parents in the simplified history on the same line as well.

Now, true parents of d87b90e4 are b5dd9d20 and 00449f99; the former changes the path you are interested in, but the latter does not. Which means in this history:

  $ git show-branch d87b90e4 00449f99 280242d1
  ! [d87b90e4] Merge branch 'js/fmt-merge-msg'
   ! [00449f99] Make git-fmt-merge-msg a builtin
    ! [280242d1] send-email: do not barf when Term::ReadLine does not
  ---
  -   [d87b90e4] Merge branch 'js/fmt-merge-msg'
  ++  [00449f99] Make git-fmt-merge-msg a builtin
  +   [b5dd9d20] Fix print-log and diff compatibility with recent vc
  +   [b5dd9d20~1] git-svn: avoid fetching files outside of the URL w
  +   [b5dd9d20~2] Improve git-peek-remote
  +   [b5dd9d20~3] t8001-annotate: fix a bash-ism in this test
  +++ [280242d1] send-email: do not barf when Term::ReadLine does not

the true history of a side branch forked at 280242d1 to 00449f99 is simplified away, and 00449f99 is replaced with the boundary commit 280242d1:

       00449f99                                   d87b90e4
         o--( branch that does not change the path) ---*
        /                                             /
    ---o----------o----------o----------o------------*
    280242d1  b5dd9d20~3  b5dd9d20~2  b5dd9d20~1  b5dd9d20

Note that 280242d1 is reachable from v1.4.2-rc1~88, so the traversal does not go beyond it (as you said --not $that).