How to Tag a single file in GIT

Question

I am very new to git. I am currently trying to get familiarized with it by using it to track changes in some excel files that I am maintaining to track some continuous activity I am involved with. All the files are in a single repository. I want to tag each file separately with their versions. Is this possible? So far what I found was the capability to tag the entire repository. If what I am trying to do is wrong, do advise me on the best practice.

Thanks in advance.

Edit

When I was doing this I deliberately deleted a previous tag to make the entire repository be tagged( as I did not find a way to tag single files) as v1.0. As I now want to reset the name of the tag with the file name and quite comfortable with the way things should happen, how can I rollback the deletion and rename the previous tag (the deleted tag)?

Answer 1

Technically you can tag the content of a single file without it's file name. But such tags are of limited use. Tags are expected to point to commits, and special tags to non-commits have very different behavior (you can't git checkout such a special tag). So I strongly suggest to never use non-commit tags.

When you want only some files to be tagged, it might be better to use a separate repo for them, or at least different branches, since git always looks at the full tree for it's operations.

If you still insist to create such a special tag you do:

> git ls-tree HEAD
040000 tree 2c186ad49fa24695512df5e41cb5e6f2d33c119b    bar
100644 blob 409940768f2a684935a7d15a29f96e82c487f439    foo.txt

> git tag my-bar-tree 2c186ad49fa24695512df5e41cb5e6f2d33c119b
> git tag my-foo-file 409940768f2a684935a7d15a29f96e82c487f439

Answer 2

You can only tag a commit, e.g. a certain snap shot in the history of your repository. However, git stores the files as blobs and what you can do is to use git notes to add a note to a blob, like this:

$ git ls-tree HEAD
100644 blob 252f7c7df5bd181536a6c9d0f9c371ce1a5dd042    .gitignore
100644 blob 8150ada74aba86c983ac3f8f63ab26aaa76fdcb7    README
100644 blob c4b1ff6dcb2a8e50727df21ced8d2872cd91af79    TODO.txt

$ git notes add -m "Adding a note to TODO" c4b1ff6dcb2a8e507
$ git notes show c4b1ff6dcb2a8e507
Adding a note to TODO

However, note that this note (no pun intended :) )is only attached to this blob, so whenever the file changes a new blob will be created (with another sha1 hash value) and the new blob will not have this note.

Answer 3

Tags are placed on specific commits as opposed to the repository as a whole as you suggest in your question.

One way of doing what you are suggesting is making sure you only commit changes to a single file with each commit, then you can tag that commit with eg. file1-v1.0 to represent v1.0 of file1.

What are you trying to represent by tagging these commits though? That will influence any advice on how to better your process.