phillco added inline comments.
INLINE COMMENTS
> martinvonz wrote in filemerge.py:744
> The documentation for filecmp.cmp() says
>
> Unless shallow is given and is false, files with identical os.stat()
> signatures are taken to be equal.
>
> Are we losing out on that optimization with this patch (when not doing
> in-memory merge). Do you have any sense of how relevant that optimization is?
Yes, and it's a bigger impact than past changes of this nature, since each
merged file, and its backup file, will be read again. So I think we need some
way to reintroduce this fast-path for two disk-backed files inside `cmp`.
I'd propose adding something like this to `filectx`:
def ondisk():
"""Returns True iff this filectx is directly backed by a file in the
filesystem and not some other abstraction. If so, callers can run system file
functions on it for better performance.
"""
It'd be True only for `workingfilectx`s and `abstractfilectx`s.
Then, inside `abstractfilectx.cmp()`, check if both the caller and other are
on-disk and use filecmp in that case.
It's a naive first take though, so improvements are appreciated.
REPOSITORY
rHG Mercurial
REVISION DETAIL
https://phab.mercurial-scm.org/D674
To: phillco, #hg-reviewers
Cc: sid0, martinvonz, mercurial-devel
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