Hi Arnaud,

Arnaud Bertrand wrote:

Today, I think that tags are not located in objects directory but in
refs/tags which is a good idea.;-)

Not precisely.  See "git help repository-layout" for more details, or
https://www.kernel.org/pub/software/scm/git/docs/user-manual.html#hacking-git
or the "git internals" chapter of https://git-scm.com/book/.

The origin of my reflection was that I wanted to find an old file.

I knew that in the past of my project, we had started to write a
driver for a device and it was abandoned. I wanted to find this file.
I knew a "key line" to search for and I knew the file was a .c file
but I didn't know the exact name.

Thanks for this context!  It's very helpful.

So, the goal was to parse all the database, find all the different .c
files and grep it to find the the driver.

Git intends to make this kind of history mining not too difficult.
You can run a command like

	git log --all -S'the key line' -- '*.c'

and it should do the right thing.  Or you can do something more
complex using something like "git rev-list --all | git diff-tree
--stdin --name-only --diff-filter=D" (to show deleted files).

Is the problem that that command is too slow?

Hope that helps,
Jonathan