Suppose you’re pulling to master. You can refer to the previous position of master by master@{1} (or even master@{10.minutes.ago}; see the specifying revisions section of the git-rev-parse man page), so that you can do things like
-
See all of the changes:
git diff master@{1} master -
See the changes to a given file:
git diff master@{1} master <file> -
See all the changes within a given directory:
git diff master@{1} master <dir> -
See the summary of changes again:
git diff --stat master@{1} master
As for your question of “how do I know if I’m on master”… well, using branches is an important part of the Git workflow. You should always be aware of what branch you’re on – if you pulled changes, you want to pull them to the right branch! You can see a list of all branches, with an asterisk by the currently checked-out one, with the command git branch. The current branch name is also printed along with the output of git status. I highly recommend skimming the man pages of commands to use – it’s a great way to slowly pick up some knowledge.
And your last question: HEAD is the name for the currently checked out branch. You can indeed use HEAD and HEAD@{1} in this context as well, but it’s a bit more robust to use the branches, since if you go and check out another branch. HEAD is now that second branch, and HEAD@{1} is now master – not what you want!
To save having to ask a lot of little questions like this, you should probably have a look at a Git tutorial. There are a million on the web, for example:
- The Pro Git book
- Git Magic
- and the 4.5 million hits on Google for “Git tutorial”