I often need to get the current SHA1 after making a new commit, so I can paste it into a cherry-pick on a different branch, or into the deploy interface. The easiest way is by adding an alias:

git config --global alias.sha "!git log -n 1 --pretty=format:"%H" | pbcopy"

A git alias is usually just a regular git command- meaning you cannnot use pipes or redirection- but starting it with the bang (!) lets you fork a shell to run the commands in. Here, I’m piping the output of git log -n 1 --pretty=format:"%H" (which outputs the SHA1 of the current tree) to pbcopy, an OS X utility that copies its input to the clipboard. I’m told that xclip -selection clipboard does the same on Ubuntu.

Now, simply type in git sha after making or checking out a commit, and you’ll have it’s hash copied to your clipboard.