Git

Amend Author Of Previous Commit

The author of the previous commit can be amended with the following command

 $ git commit --amend --author "Don Draper <ddraper@sterlingcooper.com>"

Accessing A Lost Commit

If you have lost track of a recent commit (perhaps you did a reset), you can generally still get it back. Run git reflog and look through the output to see if you can find that commit. Note the sha value associated with that commit. Let’s say it is 39e85b2. You can peruse the details of that commit with git show 39e85b2.

From there, the utility belt that is git is at your disposal. For example, you can cherry-pick the commit or do a rebase.

Caching Credentials

When public key authentication isn’t an option, you may find yourself typing your password over and over when pushing to and pulling from a remote git repository. This can get tedious. You can get around it by configuring git to cache your credentials. Add the following lines to the .git/config file of the particular project.

[credential]
    helper = cache --timeout=300

This will tell git to cache your credentials for 5 minutes. Use a much larger number of seconds (e.g. 604800) to cache for longer.

Alternatively, you can execute the command from the command line like so:

$ git config credential.helper 'cache --timeout=300'

source

Renaming A Branch

The -m flag can be used with git branch to move/rename an existing branch. If you are already on the branch that you want to rename, all you need to do is provide the new branch name.

$ git branch -m <new-branch-name>

If you want to rename a branch other than the one you are currently on, you must specify both the existing (old) branch name and the new branch name.

$ git branch -m <old-branch-name> <new-branch-name>

Resetting A Reset

Sometimes we run commands like git reset --hard HEAD~ when we shouldn’t have. We wish we could undo what we’ve done, but the commit we’ve reset is gone forever. Or is it?

When bad things happen, git-reflog can often lend a hand. Using git-reflog, we can find our way back to were we’ve been; to better times.

$ git reflog
00f77eb HEAD@{0}: reset: moving to HEAD~
9b2fb39 HEAD@{1}: commit: Add this set of important changes
...

We can see that HEAD@{1} references a time and place before we destroyed our last commit. Let’s fix things by resetting to that.

$ git reset HEAD@{1}

Our lost commit is found.

Unfortunately, we cannot undo all the bad in the world. Any changes to tracked files will be irreparably lost.

source

What Changed?

If you want to know what has changed at each commit in your Git history, then just ask git whatchanged.

$ git whatchanged

commit ddc929c03f5d629af6e725b690f1a4d2804bc2e5
Author: jbranchaud <jbranchaud@gmail.com>
Date:   Sun Feb 12 14:04:12 2017 -0600

    Add the source to the latest til

:100644 100644 f6e7638... 2b192e1... M  elixir/compute-md5-digest-of-a-string.md

commit 65ecb9f01876bb1a7c2530c0df888f45f5a11cbb
Author: jbranchaud <jbranchaud@gmail.com>
Date:   Sat Feb 11 18:34:25 2017 -0600

    Add Compute md5 Digest Of A String as an Elixir til

:100644 100644 5af3ca2... 7e4794f... M  README.md
:000000 100644 0000000... f6e7638... A  elixir/compute-md5-digest-of-a-string.md

...

This is an old command that is mostly equivalent to git-log. In fact, the man page for git-whatchanged says:

New users are encouraged to use git-log(1) instead.

The difference is that git-whatchanged shows you the changed files in their raw format which can be useful if you know what you are looking for.

See man git-whatchanged for more details.

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Git