Changing file names in git repo

It will automatically be detected as a modification and the "new" file will be added to the index, so you only need one command:

$ git mv application.py newApplication.py
$ git status
# On branch buildServer
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       renamed:    application.py -> newApplication.py

And a commit of course ..

In each commit, git records the state of your source tree, rather than whether there was a rename (or whatever) that produced that state. So, if you just rename a file normally (rather than with git mv), the output of git status will be something like:

# On branch master
# Changed but not updated:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#   deleted:    foo.txt
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   bar.txt
no changes added to commit (use "git add" and/or "git commit -a")

If you then decide that you want to record the state of the tree with that file renamed, you can stage that change with:

 git rm foo.txt
 git add bar.txt

... then git status will show you:

# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   renamed:    foo.txt -> bar.txt

... and you can commit that with git commit as usual:

git commit -m "Renamed foo.txt to bar.txt"

The important point is to bear in mind is that when git tells you that a file has been renamed when you view history, that's because it has worked out that rename must have happened by comparing the state of the tree from one version to another - it doesn't mean that a rename operation was recorded in the history.

As previous answers have explained, Git derives a file rename operation from the change in content in your source tree. To record a rename operation, Git stores both a delete and add operation, and not the rename operation itself.

As Magnus Skog pointed out git mv <filename1> <filename2> tells Git to add the content in <filename1> to <filename2> and remove <filename1> from the file tree.

As Mark Longair explained, if instead of git mv, you use shell command mv <filename1> <filename2>, Git will not detect the rename operation until you invoke git rm <filename1> and git add <filename2>.

However, another way to tell Git about rename operations with mv is to use git add --all. This command instructs Git to detect and prepare to commit all files in your workspace that differ from those in the repository, including those that you've renamed:

$ ls
a  b  c  d
$ mv d e
$ git status
# On branch master
# Changed but not updated:
#   (use "git add/rm <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#   deleted:    d
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   e
no changes added to commit (use "git add" and/or "git commit -a")
$ git add --all
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   renamed:    d -> e
#

git add --all is a very convenient way to commit a large number of files that you've renamed in your workspace using a script or bulk renaming tool, for example.