Turning micro-commits into one megacommit

When I first learned about versioning you were told to “commit often”.  On larger open source projects I’ve been painfully learning that the story is a little different — you want to squash the granularity of your commits so that there is a 1-1 commit-to-feature ratio. So – you need to distill all your micro commits into a **single** mega commit.

[update – attached a shell script to automate this at the bottom of this post]

First you need to know where “micro-commits” come from. 

Micro commits can come from (at least) two places.  In my case – they come from pulls, and from me.

1) The insidious micro-commit generator lurking within: git pull.
When you issue:

Git is actually doing TWO things for you:

– Pulling down source code from remote
– Merging it into your branch <– this is a source of a commit 🙁

2) Another micro-commit source: you.
The other micro-commits are the ones you deliberately do:

git commit -m “another teenie-tiny commit with a single semicolon in it”

 
Now – you need to know how to squash them.

 There are two rules to commit squashing:

• REBASE when you pull from remote ! This squashes your “pull” micro commits. 
• When you push to the main branch (or issue pull requests to the main branch), you should do so by CREATING a specific new branch, merging commits from your “development” branch by using the “–squash” option. 
• Note that you can automate rebasing in your .git/ config files.

Example 

 Say you have “my_feature_branch” that you want to merge into “master”.   Here is what a workflow might look like.

#Do some work
git checkout my_feature_branch
touch a
git add a
git commit -m “micro commit 1” 

#Maybe you want to pull some stuff down … heres the cleanest way to do it.
git pull origin master —rebase 
#okay… now lets do some MORE work…
touch b
git add b 
git commit -m “micro commit 2”

At this point, you have 2 commits (you would have 3 if you didn’t do the rebase).

# Now… checkout the master branch, and merge all of micro commits into one mega commit.
git checkout master
git merge —squash my_feature_branch
git commit -m “a mega commit with 2 commits worth of new stuff, which is already also merged with latest master”

Update – here’s a shell script that creates a new branch off of master and pulls your current branch’s commits into it – without creating a new commit). 

#starting at the current branch
 
#1 Parse the current branch name
Current=`git branch | grep “*” | sed -e ‘s/*//’ | sed -e ‘s/ //’`
Ext=”_squashed”
Squashed=$Current$Ext
echo “New branch is $Squashed”
 
#2 Checkout master , we will branch off of it
git checkout master
echo “Now on master…”
git branch
 
#3 Checkout the squashed branch
git branch -t $Squashed
echo “Created branch : $Squashed”
 
#4 Checkout new branch
git checkout $Squashed
echo “New branch “
git branch
 
#5 Merge with the original work branch
git merge –squash $Current
echo “Final Branch”
git branch