Recently there have been lots of new developments in the imapfw community. Lots of new people coming in for contributing under GSoC. One of the trickiest thing newcomers encounter when starting to contribute is with some git operations particularly with squashing.
This blog will guide through the basics of how to squash and also highlight
other useful options provided by the git rebase command.
Setting up the playground
For the purpose of this tutorial we will be working with a simple gist. Keep in mind gists are full-blown git repositories, but they DO NOT support folders.
- Go ahead and clone the following:
-
git clone git@gist.github.com:10ef9336a6b9c7572ada9ec6229fe9b7.git
-
- See what’s in the repo:
-
cd 10ef9336a6b9c7572ada9ec6229fe9b7 git log --graph --oneline
-
Current state
By running the last command, what we get is this:
* b68977f fix another typo word
* ac573c6 fixed a typo word
* 6102ded
As we can see, we have 2 trivial commits, that we can group as one, with the following constraints:
- Keeping changes from both the commits.
- Only show either one of the commit message, or a completely new commit message
And that’s what we call squashing
Enters git rebase
We will be using the -i option, which translates to interactive. The command has roughly the following syntax for squashing:
git rebase -i HEAD~<number-of-commits-to-squash>
Since want to squash previous 2 commits, our command should be:
git rebase -i HEAD~2
What this yields is something like this:
pick ac573c6 fixed a typo word
pick b68977f fix another typo word
# Rebase 6102ded..b68977f onto 6102ded (2 command(s))
#
# Commands:
# p, pick = use commit
# r, reword = use commit, but edit the commit message
# e, edit = use commit, but stop for amending
# s, squash = use commit, but meld into previous commit
# f, fixup = like "squash", but discard this commit's log message
# x, exec = run command (the rest of the line) using shell
#
# 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
The above output can roughly be divided into 2 categories:
- The un-commented lines (1-2)
pick ac573c6 fixed a typo word
pick b68977f fix another typo word
are exactly the commits we need to squash, so our HEAD~2 part was correct.
- The commented lines (ones starting with
#). This basically is a short documentation of what options can we use here and what they mean.
For the purpose of squashing we can see the line:
# s, squash = use commit, but meld into previous commit
That’s exactly the behavior we need.
The Squash
- We now do the necessary changes, and they should look something like this
pick ac573c6 fixed a typo word
squash b68977f fix another typo word
# Rebase 6102ded..b68977f onto 6102ded (2 command(s))
#
# Commands:
# p, pick = use commit
# r, reword = use commit, but edit the commit message
# e, edit = use commit, but stop for amending
# s, squash = use commit, but meld into previous commit
# f, fixup = like "squash", but discard this commit's log message
# x, exec = run command (the rest of the line) using shell
#
# 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
- As soon as we write this to the disk and exit, a new window editor will open with the following:
# This is a combination of 2 commits.
# The first commit's message is:
fixed a typo word
Signed-off-by: Ishan Khare <ishankhare07@gmail.com>
# This is the 2nd commit message:
fix another typo word
Signed-off-by: Ishan Khare <ishankhare07@gmail.com>
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Date: Thu Mar 31 19:00:41 2016 +0530
#
# rebase in progress; onto 6102ded
# You are currently editing a commit while rebasing branch 'master' on '6102ded'.
#
# Changes to be committed:
# modified: zen.txt
#
# Untracked files:
# output.txt
#
- We can see the 2 commits, go ahead and remove 1, edit the other one. There is NO NEED to do any changes with comments, they won’t matter. It should finally look something like this:
# This is a combination of 2 commits.
# The first commit's message is:
fix word typos
Signed-off-by: Ishan Khare <ishankhare07@gmail.com>
# This is the 2nd commit message:
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Date: Thu Mar 31 19:00:41 2016 +0530
#
# rebase in progress; onto 6102ded
# You are currently editing a commit while rebasing branch 'master' on '6102ded'.
#
# Changes to be committed:
# modified: zen.txt
#
# Untracked files:
# output.txt
#
We removed the second commit message and the sign-off which finally gives
us a single squashed commit.