Git: how to renormalize line endings in all files in all revisions?

Since Git 2.16 (Q1 2018) there is another way (other than deleting the index content), with "git add --renormalize .", which is a new and safer way to record the fact that you are correcting the end-of-line convention

See commit 9472935 (16 Nov 2017) by Torsten Bögershausen (tboegi).
^{(Merged by Junio C Hamano -- gitster -- in commit af6e0fe, 27 Nov 2017)}

add: introduce "--renormalize"

Make it safer to normalize the line endings in a repository.
Files that had been committed with CRLF will be committed with LF.

The old way to normalize a repo was like this:

# Make sure that there are not untracked files
 $ echo "* text=auto" >.gitattributes
 $ git read-tree --empty
 $ git add .
 $ git commit -m "Introduce end-of-line normalization"

The user must make sure that there are no untracked files, otherwise they would have been added and tracked from now on.

The new "add --renormalize" does not add untracked files:

$ echo "* text=auto" >.gitattributes
 $ git add --renormalize .
 $ git commit -m "Introduce end-of-line normalization"

Note that "git add --renormalize <pathspec>" is the short form for "git add -u --renormalize <pathspec>".

Note: Git 2.21 (Feb. 2019) fixes a bug related to this: "git add --ignore-errors" did not work as advertised and instead worked as an unintended synonym for "git add --renormalize", which has been fixed.

See commit 9e5da3d (17 Jan 2019) by Jeff King (peff).
^{(Merged by Junio C Hamano -- gitster -- in commit 1c41824, 05 Feb 2019)}

add: use separate ADD_CACHE_RENORMALIZE flag

Commit 9472935 (add: introduce "--renormalize", 2017-11-16, Git 2.16) taught git add to pass HASH_RENORMALIZE to add_to_index(), which then passes the flag along to index_path().
However, the flags taken by add_to_index() and the ones taken by index_path() are distinct namespaces.
We cannot take HASH_* flags in add_to_index(), because they overlap with the ADD_CACHE_* flags we already take (in this case, HASH_RENORMALIZE conflicts with ADD_CACHE_IGNORE_ERRORS).

We can solve this by adding a new ADD_CACHE_RENORMALIZE flag, and using it to set HASH_RENORMALIZE within add_to_index().
In order to make it clear that these two flags come from distinct sets, let's also change the name "newflags" in the function to "hash_flags".

Also: See commit e2c2a37 (07 Feb 2019) by Jeff King (peff).
^{(Merged by Junio C Hamano -- gitster -- in commit 9293bf6, 07 Feb 2019)}

add_to_index(): convert forgotten HASH_RENORMALIZE check

Commit 9e5da3d (add: use separate ADD_CACHE_RENORMALIZE flag, 2019-01-17) switched out using HASH_RENORMALIZE in our flags field for a new ADD_CACHE_RENORMALIZE flag.
However, it forgot to convert one of the checks for HASH_RENORMALIZE into the new flag, which totally broke "git add --renormalize".

If you just want to renormalize your current commit after having set core.autocrlf or text=auto, so you can have all the line ending normalization in one commit, run these commands:

git rm --cached -rf .
git add .

To also normalize the files in your working dir, run:

git checkout .