Git internals book

This morning I saw at my rss feed that a book called Git Internals by Scott Chacon has been opensourced. So, having an idle afternoon, I borrowed an ebook from a relative and read it while taking a sunbath (idea! Have a tablet with a electronic ink screen and vim, and program on the beach.. I’m eager to see fast enough e. ink for that!)

The first 10-15 pages of the book are about the internal cogs of git, and they are easy to read and very well explained with diagrams. I invite you to read them, because thanks to them I now understand Git very well. The rest of the book covers how to work with git, and typical commands. Some of its bits are new to me, so I have summarized them here for you and me (well, mostly for me, I doubt anyone is reading this :P).

Possible workflows for decentralized SCM systems as git

• Central repository model: better for small teams.

• Dictator and leutenant model: better for large teams. Eg: Linux kernel

• Integration manager model: community based git repos. Eg: Github

GUIs that come bundled with git

Provide simple visualization of git trees and commits:

• gitk: Tcl/Tk based browser. Will take most of the same arguments that git log will take.

• git instaweb: Without Tk. It fires up a web server running the gitweb CGI script, using lighttpd, apache, or webrick and then opens your default browser.

  • Open: git instaweb --httpd = lighttpd or apache or webrick

  • Close: git intaweb stop

Crypto signed tags

• Sign tag: git tag -s (sign with email address GPG key)

  or git tag -u <keyID> v1.0 -m "release v1.0"

• Verify signed tag: git tag -v v1.0

• push tag to remote: git push origin [tagname]

###Caring of git From time to time, you need to take care of git repos, usually the big ones. To have them healthy and running quickly:

• Garbage collection: git gc (it is possible to turn it off and on automatically).

• Fsck:

  git fsck : To know if there are unreachable or corrupted objects in the DB and fix them.

  git prune : To remove dangling objects.

Sharing repos

It is done using the git-daemon, which supports these 3 protocols:

• git: No built in integration, generally you cannot push over it.

• ssh: If an user has ssh and write access, that user can push.

• http: easy setup, you need just static web server. But to push, you need to run a DAV server.

Browse git objects(blobs) directly

• git show [object]

• git cat-file [object]

Generating patch files

• Generate: git diff master..experiment > patchFile

• Apply patch: patch -p1 patchFile patching file fileToPatch

Export a tree

git-archive: For exporting a snapshot of a git tree.

Interactive shells

git add -i: Provides an interactive shell to select files, and also allows to commit only chunk of files (useful for a patch).

git rebase -i: For complex rebasing.