Nguyen Thai Ngoc Duy wrote:
> To be honest, I have no idea what the above describes. I read 9bc454d
> (reset: add option "--keep" to "git reset" - 2010-01-19) and figured
> that --keep is like --merge except that "git diff" before and after
> the reset is exactly the same, is it? I have never used --keep before.
I use "git reset --keep" to
- discard a bad commit: git reset --keep HEAD^
- start working against a different commit:
git checkout -b topic &&
... hack hack hack without committing ... &&
: "oops, I thought I was on master but I was somewhere else" &&
git reset --keep master
The spirit of the thing[1] is:
* if the diff "HEAD -> <commit>" touch paths in which we have local
changes, error out;
* otherwise, checkout the relevant paths from <commit> but leave the
paths in which we have local changes alone.
which indeed means "git diff --cached" and "git diff" before and after
would be exactly the same. But there are some edge cases, in which
the diff "HEAD -> <commit>" makes the same change we did and the
reset --keep is still allowed.
This is totally different from --merge. The only legitimate use of
--merge is to cancel a merge you just performed, imho --- the effect
otherwise is too scary ("git add <path>; git reset --merge elsewhere"
--- bye, bye, changes made at <path>).
Hope that helps,
Jonathan
[1] Detailed semantics: for each path listed by "git diff --name-only
HEAD <commit>":
* if the worktree, index, and HEAD match, make the index and worktree
match <commit>.
* otherwise, if it is "not easy" to keep local changes, error out.
We are not going to do a three-way merge. That is,
- if the index matches neither HEAD nor <commit>, error out;
- if the index matches HEAD but not the worktree, error out.
* otherwise, it is "easy", so keep local changes.
- if the index already matches <commit>, leave the index and
worktree alone.
- if the index and worktree match HEAD, make them match the
<commit> instead.
These are the same rules used by fast-forward merges and plain
"git checkout".
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