[petsc-dev] Commit squashing in MR

[Junchao Zhang]

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
>
>
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