This repository holds the source for the elemental parts needed for a simple VCS written in Bourne shell. This is an academic exercise and should not be used for actual version control of anything critical.
The reason for this is purely heuristic: how might one approach building a DVCS like git? Once you can understand this small bit of Bourne shell, you can also understand many of the underpinnings and architectural decisions that went into git and thereby gain a sufficiently robust mental model for understanding git better.
This repo will also hold additional git training and a presentation that accompany this shell file.
- Read the source
- Play with it
- Enjoy enlightenment
Source the file:
$ source dvc.sh
This will import the shell function definitions into your current shell session.
Create an empty directory and initialize it as a repo:
$ mkdir my-repo
$ cd my-repo
$ init .
View the empty repo:
$ find .dvcsh -type f -print
Create a new file and add it into the repo:
$ echo "some file" > some-file.txt
$ add some-file.txt
View the new object and index in the repo:
$ find .dvcsh -type f -print
$ cat .dvcsh/index
Commit the changes:
$ commit "first commit"
View the commit object and other artifacts:
$ find .dvcsh -type f -print | xargs head
It would be fairly easy to make this even more git-like by adding tree objects. The diff, checkout, and tag commands are also low-hanging fruit at this point. With this one little file, we could be self-hosting and on our way to a lovely little DVCS of our own... if this weren't a purely academic exercise. Enjoy!
This shell file exports a handful of symbols into your shell:
- _hash_obj
- init
- add
- commit
- log
If you have executables or other shell functions defined, they will be clobbered until your next shell session.
I am not a Bourne shell expert. None of this code should be looked to as the right way to write Bourne shell code. I used the Bourne shell because everybody has access to it and it is fairly easy to read.