Git: Adding files and resetting

Alice creates a new repository.

Alice/> git init --template=""
Initialized empty Git repository in /home/rene/github/github/git-internals/repos/add-and-reset/Alice/.git/

She creates a file whose content is simply: foo

Alice/> echo foo > a.file

Then, she adds the file to the index.

Alice/> git add a.file

This creates a blob object.

She adds another line (bar) to the file:

Alice/> echo bar >> a.file

Alice commits the newly added file

Alice/> git commit -m "+ a.file"
[master (root-commit) 74f3684] + a.file
 1 file changed, 1 insertion(+)
 create mode 100644 a.file

Note: this commits the content of the file that was added (blob object 257cc56…), not the content of the file as it is in the working directory. Note also that the content of the working directory would be commited if Alice executed the commit with a dot: git commit . -m …

Because the commit didn't commit the file in the working directory, the file's status is modified:

Alice/> git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   a.file

no changes added to commit (use "git add" and/or "git commit -a")

Showing the content of the file as stored in the repository:

Alice/> git show HEAD:a.file
foo

Alice resets the working tree so that it matches HEAD:

Alice/> git reset --hard
HEAD is now at 74f3684 + a.file

Note: it creates .git/ORIG_HEAD

Thus, the content of a.file is foo again:

Alice/> cat a.file
foo