[petsc-dev] rebase question

[Jed Brown]

On Mon, Sep 5, 2011 at 07:56, Satish Balay <balay at mcs.anl.gov> wrote:

> Just want to point out that the same thing should happen with 'hg
> update' - or with the alternative workflow to 'hg pull --rebase' i.e
> 'hg pull; hg merge; hg commit'
>
> i.e in all the above cases - the working files get updated by
> mercurial underneath emacs.
>

Suppose you have a repository like this

@  changeset:   2:c4d14c7899e5
|  tag:         tip
|  parent:      0:c2e4f2b285da
|  user:        Jed Brown <jed at 59A2.org>
|  date:        Mon Sep 05 09:39:37 2011 +0200
|  summary:     mine
|
| o  changeset:   1:3a3076850a53
|/   user:        Jed Brown <jed at 59A2.org>
|    date:        Mon Sep 05 09:38:05 2011 +0200
|    summary:     upstream
|
o  changeset:   0:c2e4f2b285da
   user:        Jed Brown <jed at 59A2.org>
   date:        Mon Sep 05 09:37:40 2011 +0200
   summary:     initial

and suppose r2 makes a modification to a file present in r0 that was not
changed by r1. Then we could ask for rebase to not update mtime for this
file. This is not the case:

$ stat a
  File: `a'
  Size: 8               Blocks: 8          IO Block: 4096   regular file
Device: 806h/2054d      Inode: 1439054     Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     jed)   Gid: (  100/   users)
Access: 2011-09-05 09:43:07.743270567 +0200
Modify: 2011-09-05 09:42:53.809936424 +0200
Change: 2011-09-05 09:42:53.809936424 +0200
 Birth: -
$ hg rebase -s 2 -d 1


saved backup bundle to /tmp/repo-hg/.hg/strip-backup/a00050fc43a7-backup.hg
$ stat a
  File: `a'
  Size: 8               Blocks: 8          IO Block: 4096   regular file
Device: 806h/2054d      Inode: 1439054     Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     jed)   Gid: (  100/   users)
Access: 2011-09-05 09:43:18.689937868 +0200
Modify: 2011-09-05 09:43:18.689937868 +0200
Change: 2011-09-05 09:43:18.689937868 +0200
 Birth: -


If instead we merge, mtime is not updated:

$ stat a
  File: `a'
  Size: 8               Blocks: 8          IO Block: 4096   regular file
Device: 806h/2054d      Inode: 1439054     Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     jed)   Gid: (  100/   users)
Access: 2011-09-05 09:45:52.003280085 +0200
Modify: 2011-09-05 09:45:49.719946619 +0200
Change: 2011-09-05 09:45:49.719946619 +0200
 Birth: -
$ hg merge 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg commit -m merge
$ stat a
  File: `a'
  Size: 8               Blocks: 8          IO Block: 4096   regular file
Device: 806h/2054d      Inode: 1439054     Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     jed)   Gid: (  100/   users)
Access: 2011-09-05 09:45:52.003280085 +0200
Modify: 2011-09-05 09:45:49.719946619 +0200
Change: 2011-09-05 09:45:49.719946619 +0200
 Birth: -


Sean, I was wrong in our conversation in the parking lot. Git behaves the
same way:

$ echo aaa > a
repo-git$ git add a
repo-git$ git commit -m initial
[master (root-commit) ec625c5] initial
 1 files changed, 1 insertions(+), 0 deletions(-)
 create mode 100644 a
master repo-git$ echo bbb > b
repo-git$ git add b
repo-git$ git commit -m upstream
[master 740d68c] upstream
 1 files changed, 1 insertions(+), 0 deletions(-)
 create mode 100644 b
repo-git$ git checkout -b mine HEAD^
Switched to a new branch 'mine'
repo-git$ echo ccc >> a
repo-git$ git commit -am mine
[mine 6f4c2d9] mine
 1 files changed, 1 insertions(+), 0 deletions(-)
$ git log master
commit 740d68ca145ec28b3cf936d65827a64fe6a6682f
Author: Jed Brown <jed at 59A2.org>
Date:   Mon Sep 5 09:47:32 2011 +0200

    upstream

commit ec625c5bbc19b13ded14643a9f79cd0e99829313
Author: Jed Brown <jed at 59A2.org>
Date:   Mon Sep 5 09:47:21 2011 +0200

    initial
repo-git$ git log
commit 6f4c2d9d5a8a632233fc0da0139e8d4ed52c6b23
Author: Jed Brown <jed at 59A2.org>
Date:   Mon Sep 5 09:48:11 2011 +0200

    mine

commit ec625c5bbc19b13ded14643a9f79cd0e99829313
Author: Jed Brown <jed at 59A2.org>
Date:   Mon Sep 5 09:47:21 2011 +0200

    initial
repo-git$ stat a
  File: `a'
  Size: 8               Blocks: 8          IO Block: 4096   regular file
Device: 806h/2054d      Inode: 1439111     Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     jed)   Gid: (  100/   users)
Access: 2011-09-05 09:52:46.199970753 +0200
Modify: 2011-09-05 09:52:06.809968470 +0200
Change: 2011-09-05 09:52:06.809968470 +0200
 Birth: -
$ git rebase master
First, rewinding head to replay your work on top of it...
Applying: mine
$ stat a
  File: `a'
  Size: 8               Blocks: 8          IO Block: 4096   regular file
Device: 806h/2054d      Inode: 1439111     Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/     jed)   Gid: (  100/   users)
Access: 2011-09-05 09:53:00.499971581 +0200
Modify: 2011-09-05 09:53:00.496638247 +0200
Change: 2011-09-05 09:53:00.496638247 +0200
 Birth: -


If you do the rebasing with an Emacs mode, it should track which files are
changed and update them accordingly.

If you don't want to set global-auto-revert-mode, you can do something like
this

(global-set-key (kbd "C-x T") '(lambda () (interactive) (revert-buffer nil
t))) ; revert without query

to reduce the interruption caused by reverting files. It all depends how
tightly you like buffers to be associated with files.
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