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Joey Hess 2016-02-22 15:24:06 -04:00
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doc/design/adjusted_branches.mdwn
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@ -22,20 +22,21 @@ play out.]
## filtering
master adjusted/master
master adjusted/master
A
|--------------->A'
| |
|--------------->A'
| |
When generating commit A', reuse the date and author and committer of A.
This means that two users with the adjusted branch checked out and using
the same filters will get identical shas for A', and so can collaborate on
them.
When generating commit A', reuse the date of A and use a standard author,
committer, and message. This means that two users with the adjusted branch
checked out and using the same filters will get identical shas for A', and
so can collaborate on them.
## commit
When committing changes, a commit is made as usual to the adjusted branch.
So, the user can `git commit`. This does not touch the original branch yet.
So, the user can `git commit` as usual. This does not touch the
original branch yet.
Then we need to get from that commit to one with the filters reversed,
which should be the same as if the adjusted branch had not been used.
@ -43,15 +44,15 @@ This commit gets added onto the original branch.
So, the branches would look like this:
master adjusted/master
master adjusted/master
A
|--------------->A'
| |
| |C (new commit)
B - - - - - - - -
|
|--------------->B'
| |
|--------------->A'
| |
| C (new commit)
B < - - - - - - -
|
|--------------->B'
| |
Note particularly that B does not have A' or C in its history;
the adjusted branch is not evident from outside.
@ -64,70 +65,98 @@ same B' commit when they pull B.
It might be useful to have a post-commit hook that generates B and B'
and updates the branches. And/or `git-annex sync` could do it.
There may be multiple commits made to the adjusted branch before any get
applied back to the original branch. This is handled by reverse filtering
one at a time and rebasing the others on top.
master adjusted/master
A
|--------------->A'
| |
| C1
| |
| C2
master adjusted/master
A
|--------------->A'
| |
| C1
B1< - - - - - - -
|
|--------------->B1'
| |
| C2'
B2< - - - - - - -
|
|--------------->B2'
[WORKTREE: A pre-commit hook would be needed to update the staged changes,
reversing the filter before the commit is made. All the other complications
above are avoided.]
## merge
This would be done by `git annex merge` and `git annex sync`.
This would be done by `git annex merge` and `git annex sync`, with the goal
of merging origin/master into master, and updating adjusted/master.
Note that the adjusted files db needs to be updated to reflect the changes
that are merged in, for object add/remove to work as described below.
When merging, there should never be any commits present on the
adjusted/master branch that have not yet been filtered over to the master
branch. There may be staged changes, or changes in the work tree.
branch. If there are any such commits, just filter them into master before
beginning the merge. There may be staged changes, or changes in the work tree.
First filter the new commit:
master adjusted/master
origin/master adjusted/master
A
|--------------->A'
| |
| |
B
|
|---------->B'
|--------------->A'
| |
| |
B
|
|---------->B'
Then, merge that into adjusted/master:
master adjusted/master
origin/master adjusted/master
A
|--------------->A'
| |
| |
B |
| |
|----------->B'->B''
|--------------->A'
| |
| |
B |
| |
|----------->B'->B''
That will take care of updating the work tree. (If there's a merge
conflict it will happen here.)
That merge will take care of updating the work tree.
Now one extra step is needed; reset adjusted/master to use B'
(here it's important that B'' and B' have the same tree).
(What if there is a merge conflict between A' and B'? Normally such a merge
conflict should only affect the work tree/index, so can be resolved without
making a commit, but B'' may end up being made to resolve a merge
conflict.)
master adjusted/master
Once the merge is done, we have a commit B'' on adjusted/master. To finish,
adjust that commit so it does not have adjusted/master as its parent.
origin/master adjusted/master
A
|--------------->A'
| |
| |
B
|
|--------------->B'
| |
|--------------->A'
| |
| |
B
|
|--------------->B''
| |
Notice how similar this is to the commit graph above. So, merging
the same B commit from master will lead to an identical sha for B'
as the committer got.
Finally, update master to point to B''.
(What if there is a merge conflict? Then B'' won't be created yet
and the conflict is between A' and B'. User can resolve that conflict as
usual, which may lead to a commit (or perhaps they resolve the conflict
in the work tree without a commit. The conficted merge
commit is handled like any other commit to the adjusted/master branch;
it gets reverse filtered back to master and bounces back to
adjusted/master.)
Notice how similar this is to the commit graph. So, "fast-forward"
merging the same B commit from origin/master will lead to an identical
sha for B' as the original committer got.
Since the adjusted/master branch is not present on the remote, if the user
does a `git pull`, it won't merge in changes from origin/master. Which is
@ -162,14 +191,20 @@ Reversing filter #1 would mean only converting pointer files to
symlinks when the file was originally a symlink. This is problimatic when a
file is renamed. Would it be ok, if foo is renamed to bar and bar is
committed, for it to be committed as an unlocked file, even if foo was
originally locked?
originally locked? Probably.
Reversing filter #2 would mean not deleting removed files whose content was
not present. When the commit includes deletion of files that were removed
due to their content not being present, those deletions are not propigated.
When the user deletes an unlocked file, the content is still
present in annex, so reversing the filter should propigate the file
deletion.
deletion.
What if an object was sent to the annex (or removed from the annex)
after the commit and before the reverse filtering? This would cause the
reverse filter to draw the wrong conclusion. Maybe look at a list of what
objects were not present when applying the filter, and use that to decide
which to not delete when reversing it?
## push
@ -280,5 +315,3 @@ like this, at its most simple:
-- Generate a version of the commit made on the filter branch
-- with the filtering of modified files reversed.
unfilteredCommit :: Filter -> Git.Commit -> Git.Commit
isFilteredCommit :: Git.Commit -> Bool