fileset: add a lightweight file filtering language
This patch was inspired by one that Jun Wu authored for the fb-experimental
repo, to avoid using matcher for efficiency[1]. We want a way to specify what
files will be converted to LFS at commit time. And per discussion, we also want
to specify what files to skip, text diff, or merge in another config option.
The current `lfs.threshold` config option could not satisfy complex needs. I'm
putting it in a core package because Augie floated the idea of also using it for
narrow and sparse.
Yuya suggested farming out to fileset.parse(), which added support for more
symbols. The only fileset element not supported here is 'negate'. (List isn't
supported by filesets either.) I also changed the 'always' token to the 'all()'
predicate for consistency, and introduced 'none()' to improve readability in a
future tracked file based config. The extension operator was changed from '.'
to '**', to match how recursive path globs are specified. Finally, I changed
the path matcher from '/' to 'path:' at Yuya's suggestion, for consistency with
matcher. Unfortunately, ':' is currently reserved in filesets, so this has to
be quoted to be processed as a string instead of a symbol[2]. We should
probably revisit that, because it's seriously ugly. But it's only used by an
experimental extension, and I think using a file based config for LFS may drive
some more tweaks, so I'm settling for this for now.
I reserved all of the glob characters in fileset except '.' and '_' for the
extension test because those are likely valid extension characters.
Sample filter settings:
all() # everything
size(">20MB") # larger than 20MB
!**.txt # except for .txt files
**.zip | **.tar.gz | **.7z # some types of compressed files
"path:bin" # files under "bin" in the project root
[1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-December/109387.html
[2] https://www.mercurial-scm.org/pipermail/mercurial-devel/2018-January/109729.html
=== property cache ===
calllog: []
cached value (unfiltered): NOCACHE
= first access on unfiltered, should do a call
access: 0
calllog: [0]
cached value (unfiltered): 0
= second access on unfiltered, should not do call
access 0
calllog: [0]
cached value (unfiltered): 0
= first access on "visible" view, should do a call
cached value ("visible" view): NOCACHE
access: 7
calllog: [0, 7]
cached value (unfiltered): 0
cached value ("visible" view): 7
= second access on "visible view", should not do call
access: 7
calllog: [0, 7]
cached value (unfiltered): 0
cached value ("visible" view): 7
= no effect on other view
cached value ("immutable" view): NOCACHE
access: 9
calllog: [0, 7, 9]
cached value (unfiltered): 0
cached value ("visible" view): 7
cached value ("immutable" view): 9
=== unfiltered property cache ===
unficalllog: []
cached value (unfiltered): NOCACHE
cached value ("visible" view): NOCACHE
cached value ("immutable" view): NOCACHE
= first access on unfiltered, should do a call
access (unfiltered): 100
unficalllog: [100]
cached value (unfiltered): 100
= second access on unfiltered, should not do call
access (unfiltered): 100
unficalllog: [100]
cached value (unfiltered): 100
= access on view should use the unfiltered cache
access (unfiltered): 100
access ("visible" view): 100
access ("immutable" view): 100
unficalllog: [100]
cached value (unfiltered): 100
cached value ("visible" view): NOCACHE
cached value ("immutable" view): NOCACHE
= even if we clear the unfiltered cache
cached value (unfiltered): NOCACHE
cached value ("visible" view): NOCACHE
cached value ("immutable" view): NOCACHE
unficalllog: [100]
access ("visible" view): 100
unficalllog: [100, 100]
cached value (unfiltered): 100
cached value ("visible" view): NOCACHE
cached value ("immutable" view): NOCACHE
access ("immutable" view): 100
unficalllog: [100, 100]
cached value (unfiltered): 100
cached value ("visible" view): NOCACHE
cached value ("immutable" view): NOCACHE
access (unfiltered): 100
unficalllog: [100, 100]
cached value (unfiltered): 100
cached value ("visible" view): NOCACHE
cached value ("immutable" view): NOCACHE