Joseph Herlant
version 1.0.4, 2014-06-21 : Adding the --rebase option to the git pull
Note
For more informations on GIT, consult the Official git website where you can read the Pro Git book for free, watch some videos and a lot of other resources.
You can also consult the Git ready website to find more tips about this.
Another good and free book about git is Git from the bottom up.
You can also use the git help command for more informations.
And watch the online courses about git on Code school!

1. Equivalent between git and mercurial (hg) commands

Just go to this url: http://mercurial.selenic.com/wiki/GitConcepts#Command_equivalence_table

2. Dealing with git logs

To get a shorter and nice display for git commits history logs, use the "--online" option. There you’ll get the logs in a "<commit id> <Commit message>" style.

git log --oneline

Output example:

$git log --oneline
e89195d Adding a tip on asciidoc using utf-8 titles
4c666c1 Adding perl helpers for converting numbers
d13b046 Adding some stuffs to do
60a2477 Adding other perl one-liners
dfd0f8f Adding some perl monks and some todo
9596bb3 Updating todo

Or use the "--pretty=format:" formatter like this:

git log --pretty=format:"%h (%ad) [%an] - %s"

Which will output something like this:

$ git log --pretty=format:"%h (%ad) [%an] - %s"
e89195d (Sat Oct 26 20:25:21 2013 +0200) [Joseph Herlant] - Adding a tip on asciidoc using utf-8 titles
4c666c1 (Fri Oct 25 12:54:59 2013 +0200) [Joseph Herlant] - Adding perl helpers for converting numbers
d13b046 (Fri Oct 25 11:32:01 2013 +0200) [Joseph Herlant] - Adding some stuffs to do
60a2477 (Fri Oct 25 11:24:55 2013 +0200) [Joseph Herlant] - Adding other perl one-liners

Or even add graphs to get branching graphs!

git log --pretty=format:"%h [%an] %s" --decorate --graph

or

git log --oneline --graph --decorate

3. What does git rebase do?

the git rebase [branch_name] command duplicates the head version of the given branch ("branch_name") just as if you did a brand new branch and then applies all the current branch’s commit history on the top of the HEAD version of the branch.

For example, if you had a commit "A1" and "A2" in the "A" branch and you do a git rebase master with a master branch that has a commit B1 done after the "A" branch creation, your command will create a new branch from the master branch’s HEAD containing the "B1" commit, and then apply the "A1" and "A2" commit on top of this. This branch will replace the branch you’ve currently checked out (branch "A" here).

It is often better to do the following instead of git pull (which will pollute the logs with merges):

git fetch
git rebase
Note
In the latest versions of git, you also can (and should because it’s quicker) just use the --rebase option of the git pull command which does a git fetch followed by a git rebase instead of the usual git fetch and git merge combination. 
git pull --rebase

4. Edit commits

4.1. Invert the order of 2 commits

The following command will open an editor containing the last 2 commands and let you alter them, so you will be able to edit them (and change their order).

git rebase -i HEAD~2

4.2. Rename a specific commit

To change the 5th last commit, use a git rebase -i HEAD~5 and use the reword command in our editor.

4.3. Merging 2 commits

To merge the last 2 commits, open a git editor using git rebase -i HEAD~2 and use the squash command to merge one of the commits into the other.

4.4. Reverting the last commit (not already pushed)

To remove the last commit from the local repository, use :

git reset --soft HEAD^

If you also want to remove the changes that were included in the last commit (and not only the commit from the timeline) from your local repository, use the "--hard" option instead of "--soft":

git reset --hard HEAD^

4.5. Adding some stuff to the last commit

To add data to the last commit, use the "--amend" option:

git commit --amend -m "New message for the last commit I want to add data to."

4.6. Adding a particular commit from another branch

If you want to get only a particular change that is in a specific commit of another branch, use the following command (--edit is if you want to edit the commit message). Be careful, this command directly commits to the local branch!

git cherry-pick -x --signoff [--edit] <hash_of_the_commit>

If you just want to apply the local branch, not commiting it, use the "--no-commit" option:

git cherry-pick --no-commit <hash_of_the_commit>
Note
You can cherry pick multiple commit by specifying multiple hashes at the end of the line, separated by spaces.

4.7. Recover a dropped commit

Warning
This has to be done on the local repo where the drop operation (reset) has heen done.

List the logs of the local repo to retrieve the hash or the short name of the operation that preceeded the operation of dropping the commit, using:

git reflog

Or the git log --walk-reflogs if you want a more verbose mode.

Then, do a:

git reset --hard <hash_retrieved>|<short_name>

5. Dealing with branches

5.1. List remote branches

git branch -r

or, with little more cool stuffs like which branch is out of date:

git remote show origin

5.2. Cleanup removed branches

The following command will remove all the local references of branches that do not exist anymore on the remote repository. Quite handy when working on big projects that have a lot of branching activity.

git remote prune origin

5.3. Recover a deleted branch

Warning
This has to be done on the local repo where the drop operation (git branch -D|-d <branch_name>) has heen done.

List the logs of the local repo to retrieve the hash or the short name of the the last commit of the dropped branch, using:

git reflog

Or the git log --walk-reflogs if you want a more verbose mode.

Then, recreate the branch (with the same name or a new name) using:

git branch <branch_name> <hash_retrieved>|<short_name>

6. Dealing with tags

6.1. List tags

git tag

6.2. Add new tag

git tag -a <tag_name> -m "<Message>"

6.3. Delete a tag

If you want to delete a tag named "tag_I_want_to_delete" from origin, use the following commands.

# Remove from local repository
git tag -d tag_I_want_to_delete
# Push change to remote repository
git push origin :refs/tags/tag_I_want_to_delete

6.4. Push new tags

Classic git push won’t push tags.If you don’t want tags to stay only local, use the "--tags" option of the push command.

git push --tags

7. Temporarly save a branch modification without commiting

7.1. Saving

To save a current state of branch modifications (for example to go and work on another branch) but without having to commit, use the stash command.

git stash save [<stash_message>]

or without the save, it does the same thing:

git stash
Warning
This will save both the staging area and the unstaged changes. If you don’t want the staging area to be stashed, use the "--keep-index" option.
If you want also the untracked files to be stashed, use the "--include-untracked" option.

And to create a branch directly from the stash, use git stash branch <branch_name>

7.2. Listing backups

git stash list

or, to get a little bit more infos on what changes are done on each stash, use the "--stat" option (or any other option of git log command) or use the following command to get the informations on one particular stash

git stash show [<stash_name>]

7.3. Getting changes back

Either do a:

git stash apply [<stash_name>]
git stash drop [<stash_name>]   # once you don't need the backup anymore

or the following which do the both previous commands in one on the last stash:

git stash pop

8. Dealing with line endings

8.1. Using git config

If you’re on a Linux/unix machine and you want to ensure line endings are in unix format when you get committed files, use:

git config --global core.autocrlf input

If you’re on a windows machine and you want to ensure line endings will be all in windows format (\r\n), use:

git config --global core.autocrlf true

8.2. Using .gitattributes file

Put a ".gitattributes" file in your repository to manage fine-grained line feeds. For example, This .gitattributes file manages automatically line endings by default but considers .bat files to need windows-style line endings, .sh files to be unix-style and .jpg to be binary files.

*     text=auto
*.py  text
*.sh  text eol=lf
*.bat text eol=crlf
*.jpg binary

9. Using submodules

9.1. Adding submodule to a project

By default, submodules don’t checkout any branch, so you need to do it explicitly.

If the submodule you are adding is empty, use:

git submodule add <remote_repository_adress_of_submodule>
git add --all
cd <submodule_dir>
git checkout <submodule_branch>

If the module you are adding contains some things, use:

git submodule add <remote_repository_adress_of_submodule>
git submodule init    # To add the submodules to the local configuration file
git submodule update  # To checkout all configured submodule
git add --all
cd <submodule_dir>
git checkout <submodule_branch>
Note
to make a module work with Github pages, you have to use the HTTPS:// version to add the submodule!

9.2. Cloning a project with submodules

git clone <parent_repository>
git submodule init    # To add the submodules to the local configuration file
git submodule update  # To checkout all configured submodule
cd <submodule_dir>
git checkout <submodule_branch>

9.3. Pulling submodules

git submodule update
cd <submodule_dir>
git checkout <submodule_branch>

9.4. Integrating commits done outside of any branches

When you forget to checkout your submodules and you commit your submodules, these commits don’t get into any branch, so you’ll need to do:

git checkout <branch_name>
git merge <hash_of_the_unbranched_commit>

9.5. Pushing submodules

Important
When commiting submodules, you also need to commit the parent project to ensure it point to the latest version of the submodule.

You can ensure to push your submodules using the "--recurse-submodules" option:

git push --recurse-submodules=on-demand

You can use alias to shorten this:

git config --global alias.pushall "push --recurse-submodules=on-demand"
git pushall     # Uses your newly created alias

10. Creating tarball from a branch or tag

Creates a gzipped tarball of a specific branch or tag in the parent directory:

git archive -o ../<my_package>_<my_version>.tar.gz <branch_name>|<tag_name>

To get the recognized files format, use the git archive --list command:

$ git archive --list
tar
tgz
tar.gz
zip