Skip to main content

A Better Way to Git Push to Deploy (updateInstead & push-to-checkout)

Wow, nearly a year since my last post. I was sort of thinking it would be something more profound, but here goes: Git recently (with version 2.3) introduced a way of easily pushing changes into a remote non-bare repository, a.k.a. push-to-deploy. The old way would be to have a post-receive hook run some update logic which would do some procedure to update a non-bare repository. There now is a simple way of configuring the target repository to update its work tree instead upon being pushed to.

Now, pushing to the target repo may fail in cases where it has been modified, so soon after, a new push-to-checkout hook was introduced to deal with this, but it will only take effect in Git 2.4. I'll show how to set up both below.

Surprisingly, when searching for "push-to-checkout", I found very few articles about this, even though it was loudly mentioned on the GitHub blog (twice, and on StackOverflow, of course). So here's another one for the googles. Besides, I just wrote this whole example on the Git Users Mailing list and figured I'd repeat it here.

Note that as it happens, I've never found myself in the sorry position of having to deploy this way in real life (real developers package their distributables), so don't take my word this being the way to do it on production systems.

Note that Git version must be >= 2.3 for this to work at all, and must be 2.4 in order for the push-to-checkout hook to take effect.
[master][~/temp/foo-web]$ git --version 
git version 2.3.6 

Take some random repo and clone it to a "remote" location:
[~/temp]$ git clone foo foo-web 
Cloning into 'foo-web'...done.

So, let's pretend that this non-bare repository is on our web-host:
[~/temp]$ cd foo-web

Configure to update on incoming pushes:
[master][~/temp/foo-web]$ git config receive.denyCurrentBranch updateInstead

Create the hook:
[master][~/temp/foo-web]$ vim .git/hooks/push-to-checkout

Contents of the push-to-checkout hook, as exemplified in the test here:

/bin/sh
echo >&2 updating from $(git rev-parse HEAD)
echo >&2 updating to "$1"

git update-index -q --refresh && git read-tree -u -m HEAD "$1" || {
    status=$?
    echo >&2 read-tree failed
    exit $status
}

Make the hook executable
[master][~/temp/foo-web]$ chmod +x .git/hooks/push-to-checkout

Now let's take it for a spin. Go back to the original repo:
[master][~/temp/foo-web]$ cd .. 
[~/temp]$ cd foo 
[master][~/temp/foo]$ git remote add web ../foo-web 
[master][~/temp/foo]$ git push web master 
Everything up-to-date

OK, that wasn't very impressive. Make some changes first, a new file heya.txt for example:
[master][~/temp/foo]$ echo `random_word` > heya.txt; git add .;git commit -m `random_word` 
[master b6765e2] overpaint 1 file changed, 1 insertion(+) create mode 100644 heya.txt

Away we go:
[master][~/temp/foo]$ git push web master 
Counting objects: 3, done. 
Delta compression using up to 4 threads. 
Compressing objects: 100% (2/2), done. 
Writing objects: 100% (3/3), 322 bytes | 0 bytes/s, done. 
Total 3 (delta 0), reused 0 (delta 0) 
To ../foo-web 
   eb2711a..b6765e2  master -> master 
Push succeeded! Now, let's see if our new file arrived OK:
[master][~/temp/foo]$ cd .. 
[~/temp]$ cd foo-web

Tada!
[master][~/temp/foo-web]$ ls 
README   foo      heya.txt



Popular posts from this blog

Encrypting and Decrypting with Spring

I was recently working with protecting some sensitive data in a typical Java application with a database underneath. We convert the data on its way out of the application using Spring Security Crypto Utilities. It "was decided" that we'd be doing AES with a key-length of 256, and this just happens to be the kind of encryption Spring crypto does out of the box. Sweet!

The big aber is that whatever JRE is running the application has to be patched with Oracle's JCE in order to do 256 bits. It's a fascinating story, the short version being that U.S. companies are restricted from exporting various encryption algorithms to certain countries, and some countries are restricted from importing them.

Once I had patched my JRE with the JCE, I found it fascinating how straight forward it was to encrypt and decrypt using the Spring Encryptors. So just for fun at the weekend, I threw together a little desktop app that will encrypt and decrypt stuff for the given password and sa…

Managing dot-files with vcsh and myrepos

Say I want to get my dot-files out on a new computer. Here's what I do:

# install vcsh & myrepos via apt/brew/etc
vcsh clone https://github.com/tfnico/config-mr.git mr
mr update

Done! All dot-files are ready to use and in place. No deploy command, no linking up symlinks to the files. No checking/out in my entire home directory as a Git repository. Yet, all my dot-files are neatly kept in fine-grained repositories, and any changes I make are immediately ready to be committed:

config-atom.git
    -> ~/.atom/*

config-mr.git
    -> ~/.mrconfig
    -> ~/.config/mr/*

config-tmuxinator.git  
    -> ~/.tmuxinator/*

config-vim.git
    -> ~/.vimrc
    -> ~/.vim/*

config-bin.git   
    -> ~/bin/*

config-git.git          
    -> ~/.gitconfig

config-tmux.git  
    -> ~/.tmux.conf    

config-zsh.git
    -> ~/.zshrc

How can this be? The key here is to use vcsh to keep track of your dot-files, and its partner myrepos/mr for operating on many repositories at the same time.

I discovere…

Always use git-svn with --prefix

TLDR: I've recently been forced back into using git-svn, and while I was at it, I noticed that git-svn generally behaves a lot better when it is initialized using the --prefix option.

Frankly, I can't see any reason why you would ever want to use git-svn without --prefix. It even added some major simplifications to my old git-svn mirror setup.

Update: Some of the advantages of this solution will disappear in newer versions of Git.

For example, make a standard-layout svn clone:

$ git svn clone -s https://svn.company.com/repos/project-foo/

You'll get this .git/config:

[svn-remote "svn"]
        url = https://svn.company.com/repos/
        fetch = project-foo/trunk:refs/remotes/trunk
        branches = project-foo/branches/*:refs/remotes/*
        tags = project-foo/tags/*:refs/remotes/tags/*

And the remote branches looks like this (git branch -a):
    remotes/trunk
    remotes/feat-bar

(Compared to regular remote branches, they look very odd because there is no remote name i…

The Best Log Viewer Ever

This is what it looks like when I want to have a look through the logfile, to see what a user did on one of our machines one day:


Read the whole story about how it works on the Viaboxx Systems blog (and upvote on DZone!).

Microsoft ups their Git efforts another notch

This week Microsoft announced first class Git support embedded in the coming version of Visual Studio.

Now, it's not completely shocking. We could have seen it coming since Microsoft started offering Git repos on CodePlex, and more recently offering a Git client for TFS. In any case, these are some big news. Scott Hanselman weighs on some features and some more background here.

For those who are a bit unaware of what the Git situation on Windows looks like these days, I've dotted down these notes:
Some explanation on these:

msysGit has long been The Way to use Git on Windows. It's basically a port of Git itself, so it's a command-line tool.GitExtensions (includes Visual Studio integration), TortoiseGit, Git Shell, posh-git and most other tools are powered by msysGit.libgit2 is a native library for doing Git stuff. It is developed completely separate from Git itself. The above tools could (and should) probably use libgit2 instead of hooking onto and around msysGit.Github…