Git - personal - cheat sheet

Hosting a git repo

• cd to the folder containing the repository
• git daemon --base-path=. --export-all --reuseaddr --informative-errors --verbose

• git clone git://<ip.ip.ip.ip>/<reponame>

• Taming the git daemon http://railsware.com/blog/2013/09/19/taming-the-git-daemon-to-quickly-share-git-repository/

Adding a remote

• git remote add <remotename> git://127.0.0.1/project_name

After that

* git fetch <remotename>
* get pull <remotename> <branch name in the remote>

Setup A Local gitignore without messing up the project config

• http://vinitkumar.me/gcode/2014/02/14/setup-a-local-gitignore-without-messing-up-project.html

• Some IDE and Editors create some files which are very specific developer’s environment.
• They need to be ignored by git.
• But we cannot patch .gitignore. It will effect the entire dev team
• Here is the trick..

• go to: cd .git/info/

  There should be a file called exclude. Fill it up with the files and directories you want it to ignore such as

  • *.swp,
  • ~*

git push & fetch

• A good article explaining git and also fetch and pull
• http://longair.net/blog/2009/04/16/git-fetch-and-merge/

Tracking Branches and remote tracking branches

• http://www.gitguys.com/topics/tracking-branches-and-remote-tracking-branches/

Compiling and Installing Git on the Ubuntu

• make prefix=/usr/local
• sudo make install prefix=/usr/local

Other Internals hacking

• https://git-scm.com/book/en/v2/Git-Internals-Git-Objects

• echo ‘test content’

  git hash-object -w –stdin

  • generate a hash object using the content from stdin
  • -w to write the blob into the git repository at .git/objects/here
  • –stdin to read from std input
  • d670460b4b4aece5915caf5c68d12f560a9fe3e4
• git cat-file -p d670460b4b4aece5915caf5c68d12f560a9fe3e4
  • display the contents of the blob object identified by the hash-tag
  • -p –> pretty print
  • -t –> type of the object
• git cat-file -p master^{tree}
  • pretty print the master(commit)’s tree object
• git update-index –add –cacheinfo 100644 83baae61804e65cc73a7201a7252750c76066a30 test.txt
  • –add –> adding to index
  • –cacheinfo –> adding entry from the git object database
  • 100644 –> blob type plain/exe/link etc
  • 83baae61804e65cc73a7201a7252750c76066a30 –> blob identifier
  • test.txt –> entry name for the corresponding blob (that name need be present on the disk)
  • this command doesn’t create any entry/file in the .git repository. TODO: where does it store this information
• git write-tree
  • this command emits a hash-tag of the tree-object
  • writes the contens of the index into a tree-object
  • to read this tree-object use > git cat-file -p > 100644 blob 83baae61804e65cc73a7201a7252750c76066a30 test.txt > git cat-file -t > tree
• git commit-tree

  • echo ‘first commit’

    git commit-tree d8329 -> commit object for the first tree

  • echo ‘second commit’

    git commit-tree 3c4e9c -p --> another commit with the pointer to previous commit

  • echo ‘third commit’

    git commit-tree 3c4e9c -p -> another commit

• git log

• programmatically generating a blob object (using ruby) # code content = "hello there" header = "blob #{content.length}\0" store = header+content require 'digest/sh1' # hash tag generation based on the stored content which is header + content sha1 = Digest::SHA1.hexdigest(store) require 'zlib' # using the sha1 as filename/path to store the content # content is zipped and stored zlib_content = Zlib::Deflate.deflate(store) path = '.git/objects/' + sha1[0,2] + '/' + sha1[2,38] require 'fileutils' FileUtils.mkdir_p(File.dirname(path)) File.open(path, 'w') { |f| f.write zlib_content}
  • that’s it, a valid git blob object will be created
  • all git objects (blob,tree,commit) are generated in a similar manner
  • blob objects can contain any content
  • commit and tree objects have some more formatting/structural requirements