Managing Files - Git Recipes - page 119

Figure 4-2 . The procedure of committing a modified file using the staging area
Two lettered states _M and M_ provide information about the state of the file in the
staging area and in the working directory.
The state _M means that:
• The first character (space): the file was not added to the staging area.
• The second character ( M ): the file was modified in the working directory.
The state M_ can be interpreted as:
• The first character ( M ): the file was added to the staging area.
• The second character (space): the state of the file in the staging area is
identical as the state of the file in the working directory.
If you want to reverse the state M_ again to _M you can use:
$ git checkout -- [filename]
4-3. Committing a modified file
Problem
You want to modify and commit a file that has already been committed. You want to
perform this operation using only the $ git commit command.