Tuesday, December 11, 2012

The Foolproof Git Setup

A confused Git user.
There was a recent complaint on Git User mailing list. Quote:
Why do I have to be a source control engineer just to be a software developer?
Now, the main issue of this poor person is that his organization has failed to on-board him into his job. They told him to use Git, but didn't give him the means to do so productively (as far as we know, anyway).

What I started wondering was: Could his employer somehow have set up Git for him so that he could work with it just as easily as with Subversion?

Given a prepared .gitconfig with all the aliases and configurations that you wanted, could you really dumb down Git so much that it would be analogous to the simpleness of SVN?

Well, here's my take on it: To a certain degree: yes. If you could narrow down Git to do the most typical two SVN commands:
  • update (pull without merging), and
  • commit (with push)
.. that would help a lot.

Dumbing down pull

The first step would be to make git pull as stupid as an svn update - always rebase local commits on top of the ones being fetched:

git config --global pull.rebase true

The above setup has a weakness though. If pull-rebase runs into a conflict, even if there is only one local commit to rebase -  you get stuck in rebase mode and you have to start figuring out what Git wants you to do. This is what it looks like (and I can see why newcomers still find Git scary when I look at this):

  ~/temp/bar/[master]>git pull
remote: Counting objects: 5, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 2), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
From /Users/tfnico/temp/foo
   24b3b7f..4705398  master     -> origin/master
First, rewinding head to replay your work on top of it...
Applying: A random commit message: makeshiftness
Using index info to reconstruct a base tree...
M readme.txt
Falling back to patching base and 3-way merge...
Auto-merging readme.txt
CONFLICT (content): Merge conflict in readme.txt
Failed to merge in the changes.
Patch failed at 0001 A random commit message: makeshiftness
The copy of the patch that failed is found in:
   /Users/tfnico/temp/bar/.git/rebase-apply/patch

When you have resolved this problem, run "git rebase --continue".
If you prefer to skip this patch, run "git rebase --skip" instead.
To check out the original branch and stop rebasing, run "git rebase --abort".

That's a lot of text for one little conflict.

While SVN will present all conflicts at once, Git will insist you handle them one commit at a time, which is nicer, but still enters you into rebase-mode where you have to go git rebase --continue when conflicts have been resolved.

So, until I can figure out a way around that, you'll have to teach your newcomer at least enough to be able to resolve conflicts, do git add <resolved file> and git rebase --continue.

OR, we go back to the drawing board.

There must be a better way

I realized this after trying to publish this blog-post, and by the time I realized it hadn't gone live, I had a better idea.

What if we just squash all local commits into being changes in the work tree?

We could make an alias: git update - which does the following

  1. git reset --soft origin/master
  2. git stash
  3. git pull
  4. git stash pop
This would essentially guarantee that any conflicts occur after we pop the stash. This is essentially the same behavior as SVN update. Here's the alias:

git config alias.update "!git reset --soft origin/master && git stash && git pull && git stash pop"

Of course this would mean that we lose the commit messages of any local commits, but that wouldn't be a problem if we also implemented the next step:

Some very pushy commits


Next up, I would imitate svn commit by automatically pushing after each commit by configuring up this post-commit hook (in .git/hooks/post-commit):

#!/bin/sh
git push

Voila. Every commit is immediately pushed away, and if there are remote changes, you have to update first. Just like in SVN.

(I know SVN will allow you to commit anyway if there are no conflicts, but I don't think that's a good idea. We could actually script our way into this too, by detecting the rejection, doing an update, and then commit again with the same commit message unless there are any conflicts.).

That's it

These two adaptions would actually go a long way, until the user wants to get into stuff like branching, and by that time he should be ready to learn to use Git properly anyway.

We could maybe alias git add to git resolve. We could also maybe wrap Git in a script and somehow capture the output messages to make them more readable and SVN-like. In the end, I guess there's also a limit to how much energy we should put into making training wheels for people..

Oh, on a final note, there's an old related project called EasyGit. They wrap Git itself and provide a smoother experience for people coming from SVN. They're not as hardline as my two adaptions above though.