Carl Worth <cworth@xxxxxxxxxx> writes:
> Yes. We're identifying the core underlying technical difference behind
> the recent discussion. Namely bzr treats one parent as special, (the
> parent that was the branch tip previously). And this special treatment
> eliminates the ability to fast-forward,
No.
bzr could trivially do fast-forward too. It's an explicit design
decision to have two separate commands.
> adds merge commits that wouldn't exist with fast forwarding,
They don't exist either with "pull".
The difference between bzr and git is smaller than you think on this
point I believe.
> There's a bit more to it than that though. The git command named
> "pull" will perform a fast-forward if possible, but will create a
> merge commit if necessary. For example:
The bzr command "pull" will do a fast-forward if possible, but will
refuse to continue and ask you to create the merge commit with other
commands if necessary.
> a a a
> | pulls | and fast-forwards to |
> b b b
> | |
> c c
Same as bzr.
> whereas:
>
> a a a
> | pulls | and creates a merge / \
> b c b c
> \ /
> m
Here, bzr will refuse to pull. It will say "branches have diverged"
and tell you to use merge.
Then, you'll do
$ bzr merge
# optionally "bzr status"
$ bzr commit -m "merged such or such thing"
So, "git pull" seems roughly equivalent to something like
$ bzr pull || (bzr merge; bzr commit -m merge)
> So I'm curious. What does bzr pull do in the case of divergence like
> this? (And this is the "numbers will be changed" case, by the way).
Not yet. The "numbers will be changed" is if b pulls, right after.
Then, one other difference is in the UI. bzr shows you commits in a
kind of hierarchical maner, like (fictive example, that's not the real
exact format).
$ bzr log
commiter: upstream@xxxxxxxxxxxxxx
message:
merged the work on a feature
------
commiter: contributor@xxxxxxxx
message:
prepared for feature X
------
commiter: contributor@xxxxxxxx
message:
implemented feature X
------
commiter: contributor@xxxxxxxx
message:
added testcase for feature X
------
commiter: upstream@xxxxxxxxxxxxxx
message:
something else
No big difference in the model either, but it probably reveals a
different vision of what "history" means.
--
Matthieu
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