[petsc-dev] Commit squashing in MR

[Satish Balay]

On Wed, 3 Mar 2021, Mark Adams wrote:

> On Tue, Mar 2, 2021 at 11:02 PM Barry Smith <bsmith at petsc.dev> wrote:
> 
> >
> >
> > On Mar 2, 2021, at 9:24 PM, Mark Adams <mfadams at lbl.gov> wrote:
> >
> > Ah, 'git graph' I will try that next time.
> >
> > I use 'git rebase -i HEAD~N', but you need an N.
> >
> > After you 'git rebase origin/main' you get other commits interspersed in
> > with yours,
> >
> >
> >    I do not get this. I thought that rebasing with main put all the main
> > changes in before your commits. I have never seen any interspersed, so I do
> > not understand this.
> >
> 
> Humm, I'm not sure. The important thing is that you will hit main commits
> and you don't want to touch those or the first of your commits.

Best to think of 'squash (rebase -i (squash))' as different from 'rebase over branch'

Sure you can club both operations - assuming that's the intention.

In some cases its preferable to only do the squash - and not rebase
(over main). For ex: when you successfully run a test pipeline - best
to do 'squash-only' (after testing) to keep the test results current.

Satish

> 
> 
> >
> >   Barry
> >
> > so I try to rebase -i before rebasing over main. Then rebase over main and
> > you have a clean and updated branch.
> >
> > Pick N to be large enough to cover the commits that you want to clean up.
> > Don't touch the ones that are not yours from main, the last time you
> > rebased over main.
> >
> > On Tue, Mar 2, 2021 at 10:02 PM Junchao Zhang <junchao.zhang at gmail.com>
> > wrote:
> >
> >> I am a naive git user, so I use interactive git rebase.  Suppose I am on
> >> the branch I want to modify,
> >>
> >> 1) Use git graph to locate an upstream commit to be used as the base
> >> $ git graph
> >> * 0d5433e9 (HEAD -> jczhang/sf-change-api) SF: rename SFCreateEmbeddedSF
> >> to SFCreateEmbeddedRootSF
> >> * e7314fbb SF: add an MPI_Op argument to SFBcast
> >> * 83df288d Replace MPIU_REPLACE with MPI_REPLACE
> >> *   b434c516 Merge branch
> >> 'barry/2021-02-02/petscsf-communication-specific' into 'main'
> >> |\
> >> | * 62152ded (barry/2021-02-02/petscsf-communication-specific)
> >> PetscSFView() never called viewer for the specific type (bug), hence many
> >> output files were incorrect.
> >> * |   a4f5d9b4 Merge branch 'jose/upgrade-magma' into 'main'
> >>
> >> 2) Suppose we choose b434c516 as the base. All commits we want to squash
> >> are after it.  Do interactive git rebase. It shows a screen for you to
> >> edit.  Read the help, which is helpful for new users
> >>   $ git rebase -i b434c516
> >> pick 83df288d Replace MPIU_REPLACE with MPI_REPLACE
> >> pick e7314fbb SF: add an MPI_Op argument to SFBcast
> >> pick 0d5433e9 SF: rename SFCreateEmbeddedSF to SFCreateEmbeddedRootSF
> >>
> >> # Rebase b434c516..0d5433e9 onto b434c516 (3 commands)
> >> #
> >> # Commands:
> >> # p, pick <commit> = use commit
> >> # r, reword <commit> = use commit, but edit the commit message
> >> # e, edit <commit> = use commit, but stop for amending
> >> # s, squash <commit> = use commit, but meld into previous commit
> >> # f, fixup <commit> = like "squash", but discard this commit's log message
> >> # x, exec <command> = run command (the rest of the line) using shell
> >> # b, break = stop here (continue rebase later with 'git rebase
> >> --continue')
> >> # d, drop <commit> = remove commit
> >> # l, label <label> = label current HEAD with a name
> >> # t, reset <label> = reset HEAD to a label
> >> # m, merge [-C <commit> | -c <commit>] <label> [# <oneline>]
> >> # .       create a merge commit using the original merge commit's
> >> # .       message (or the oneline, if no original merge commit was
> >> # .       specified). Use -c <commit> to reword the commit message.
> >> #
> >> # These lines can be re-ordered; they are executed from top to bottom.
> >> #
> >> # If you remove a line here THAT COMMIT WILL BE LOST.
> >> #
> >> # However, if you remove everything, the rebase will be aborted.
> >> #
> >> # Note that empty commits are commented out
> >>
> >> 3) Suppose we want to squash the last two commits to 83df288d, replace
> >> their pick with s (or f, see the help for difference), save and exit the
> >> screen
> >> pick 83df288d Replace MPIU_REPLACE with MPI_REPLACE
> >> s e7314fbb SF: add an MPI_Op argument to SFBcast
> >> s 0d5433e9 SF: rename SFCreateEmbeddedSF to SFCreateEmbeddedRootSF
> >>
> >> A new screen shows up
> >>
> >> # This is a combination of 3 commits.
> >> # This is the 1st commit message:
> >>
> >> Replace MPIU_REPLACE with MPI_REPLACE
> >>
> >> Since we believe all MPI implementations support MPI_REPLACE
> >>
> >> # This is the commit message #2:
> >>
> >> SF: add an MPI_Op argument to SFBcast
> >>
> >> # This is the commit message #3:
> >>
> >> SF: rename SFCreateEmbeddedSF to SFCreateEmbeddedRootSF
> >>
> >> # Please enter the commit message for your changes. Lines starting
> >> # with '#' will be ignored, and an empty message aborts the commit.
> >>
> >> 4) Edit the commit message as you want, save and exit, done!
> >>
> >> --Junchao Zhang
> >>
> >>
> >> On Tue, Mar 2, 2021 at 6:19 PM Blaise A Bourdin <bourdin at lsu.edu> wrote:
> >>
> >>> Hi,
> >>>
> >>> This is not technically a petsc question.
> >>> It would be great to have a short section in the PETSc integration
> >>> workflow document explaining how to squash commits in a MR for git-impaired
> >>> developers like me.
> >>>
> >>> Anybody wants to pitch in, or explain me how to do this?
> >>>
> >>> Regards,
> >>> Blaise
> >>>
> >>> --
> >>> A.K. & Shirley Barton Professor of  Mathematics
> >>> Adjunct Professor of Mechanical Engineering
> >>> Adjunct of the Center for Computation & Technology
> >>> Louisiana State University, Lockett Hall Room 344, Baton Rouge, LA
> >>> 70803, USA
> >>> Tel. +1 (225) 578 1612, Fax  +1 (225) 578 4276 Web
> >>> http://www.math.lsu.edu/~bourdin
> >>>
> >>>
> >
>