In a topic branch workflow, you often want to find the latest commit that
merged a side branch that touched a particular area of the system, so that
a new topic branch to work on that area can be forked from that commit.
For example, I wanted to find an appropriate fork-point to queue Luke's
changes related to git-p4 in contrib/fast-import/.
"git log --first-parent" traverses the first-parent chain, and "-m --stat"
shows the list of paths touched by commits including merge commits. We
could ask the question this way:
# What is the latest commit that touched that path?
$ git log --first-parent --oneline -m --stat master |
sed -e '/^ contrib\/fast-import\/git-p4 /q' | tail
The above finds that 8cbfc11 (Merge branch 'pw/p4-view-updates',
2012-01-06) was such a commit.
But a more natural way to spell this question is this:
$ git log --first-parent --oneline -m --stat -1 master -- \
contrib/fast-import/git-p4
Unfortunately, this does not work. It finds ecb7cf9 (git-p4: rewrite view
handling, 2012-01-02). This commit is a part of the merged topic branch
and is _not_ on the first-parent path from the 'master':
$ git show-branch 8cbfc11ecb7cf9
! [8cbfc11] Merge branch 'pw/p4-view-updates'
! [ecb7cf9] git-p4: rewrite view handling
--
- [8cbfc11] Merge branch 'pw/p4-view-updates'
+ [8cbfc11^2] git-p4: view spec documentation
++ [ecb7cf9] git-p4: rewrite view handling
The problem is caused by the merge simplification logic when it inspects
the merge commit 8cbfc11. In this case, the history leading to the tip of
'master' did not touch git-p4 since 'pw/p4-view-updates' topic forked, and
the result of the merge is simply a copy from the tip of the topic branch
in the view limited by the given pathspec. The merge simplification logic
discards the history on the mainline side of the merge, and pretends as if
the sole parent of the merge is its second parent, i.e. the tip of the
topic. While this simplification is correct in the general case, it is at
least surprising if not outright wrong when the user explicitly asked to
show the first-parent history.
Here is an attempt to fix this issue, by not allowing us to compare the
merge result with anything but the first parent when --first-parent is in
effect, to avoid the history traversal veering off to the side branch.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
////////////////////////////////////////////////////////////////
GIT - the stupid content tracker
////////////////////////////////////////////////////////////////
"git" can mean anything, depending on your mood.
- random three-letter combination that is pronounceable, and not
actually used by any common UNIX command. The fact that it is a
mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the
dictionary of slang.
- "global information tracker": you're in a good mood, and it actually
works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks
Git is a fast, scalable, distributed revision control system with an
unusually rich command set that provides both high-level operations
and full access to internals.
Git is an Open Source project covered by the GNU General Public License.
It was originally written by Linus Torvalds with help of a group of
hackers around the net. It is currently maintained by Junio C Hamano.
Please read the file INSTALL for installation instructions.
See Documentation/gittutorial.txt to get started, then see
Documentation/everyday.txt for a useful minimum set of commands, and
Documentation/git-commandname.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with "man gittutorial" or "git help tutorial", and the
documentation of each command with "man git-commandname" or "git help
commandname".
CVS users may also want to read Documentation/gitcvs-migration.txt
("man gitcvs-migration" or "git help cvs-migration" if git is
installed).
Many Git online resources are accessible from http://git-scm.com/
including full documentation and Git related tools.
The user discussion and development of Git take place on the Git
mailing list -- everyone is welcome to post bug reports, feature
requests, comments and patches to git@vger.kernel.org. To subscribe
to the list, send an email with just "subscribe git" in the body to
majordomo@vger.kernel.org. The mailing list archives are available at
http://marc.theaimsgroup.com/?l=git and other archival sites.
The messages titled "A note from the maintainer", "What's in
git.git (stable)" and "What's cooking in git.git (topics)" and
the discussion following them on the mailing list give a good
reference for project status, development direction and
remaining tasks.
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