Re: [V9fs-developer] [GIT PULL] 9p Patches for 2.6.23 merge window

From: Linus Torvalds
Date: Mon Jul 16 2007 - 12:30:01 EST




On Sun, 15 Jul 2007, Latchesar Ionkov wrote:
>
> I thought that it is not a good idea to keep the v9fs_ prefix for code
> that is in different places (fs/9p and net/9p). If keeping the old
> prefix is more acceptable, I can create a new patch without the
> "v9fs_"->"p9_" renames.

It's fine, I don't care *that* much, and I already pulled. If it had been
something more central, I'd have rejected it, but soemthing as specialized
as the Plan9 fs, I just wanted to point out that this is now how we should
do things.

In other words: when doing renames it is generally *much* nicer to do a
100% rename (perhaps with just _trivial_ changes to make it compile - the
include statements etc change, and maybe you want to change the name in
the comment header too).

Doing "move the code and change it at the same time" is considered bad
form. Movement diffs are much harder to read anyway (a traditional diff
will show it as a new-file + delete, of course), so the general rule is:

- move code around _without_ modifying it, so that code movement (whether
it's a whole file, or just a set of functions between files) doesn't
really introduce any real changes, and is easier to look through the
changes.

- do the actual changes to the code as a separate thing.

This should be true in just about *any* development model, and it's
especially true in Linux, where patches are the main way people
communicate.

And when using git, the whole "keep code movement separate from changes"
has an even more fundamental reason: git can track code movement (again,
whether moving a whole file or just a function between files), and doing a
"git blame -C" will actually follow code movement between files. It does
that by similarity analysis, but it does mean that if you both move the
code *and* change it at the same time, git cannot see that "oh, that
function came originally from that other file", and now you get worse
annotations about where code actually originated.

So next time, please don't move code and change it at the same time.

Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/