view mercurial/help/filesets.txt @ 40777:3c842749debc

match: avoid translating glob to matcher multiple times for large sets

For hgignore with many globs, the resulting regexp might not fit under the 20K
length limit. So the patterns need to be broken up in smaller pieces.

Before this change, the logic was re-starting the full process from scratch
for each smaller pieces, including the translation of globs into regexp.
Effectively doing the work over and over.

If the 20K limit is reached, we are likely in a case where there is many such
glob, so exporting them is especially expensive and we should be careful not
to do that work more than once.

To work around this, we now translate glob to regexp once and for all. Then,
we assemble the resulting individual regexp into valid blocks.

This raises a very significant performance win for large `.hgignore file`:

Before: ! wall 0.153153 comb 0.150000 user 0.150000 sys 0.000000 (median of 66)
After:  ! wall 0.059793 comb 0.060000 user 0.060000 sys 0.000000 (median of 100)

Mercurial supports a functional language for selecting a set of
files.

Like other file patterns, this pattern type is indicated by a prefix,
'set:'. The language supports a number of predicates which are joined
by infix operators. Parenthesis can be used for grouping.

Identifiers such as filenames or patterns must be quoted with single
or double quotes if they contain characters outside of
``[.*{}[]?/\_a-zA-Z0-9\x80-\xff]`` or if they match one of the
predefined predicates. This generally applies to file patterns other
than globs and arguments for predicates. Pattern prefixes such as
``path:`` may be specified without quoting.

Special characters can be used in quoted identifiers by escaping them,
e.g., ``\n`` is interpreted as a newline. To prevent them from being
interpreted, strings can be prefixed with ``r``, e.g. ``r'...'``.

See also :hg:`help patterns`.

Operators
=========

There is a single prefix operator:

``not x``
  Files not in x. Short form is ``! x``.

These are the supported infix operators:

``x and y``
  The intersection of files in x and y. Short form is ``x & y``.

``x or y``
  The union of files in x and y. There are two alternative short
  forms: ``x | y`` and ``x + y``.

``x - y``
  Files in x but not in y.

Predicates
==========

The following predicates are supported:

.. predicatesmarker

Examples
========

Some sample queries:

- Show status of files that appear to be binary in the working directory::

    hg status -A "set:binary()"

- Forget files that are in .hgignore but are already tracked::

    hg forget "set:hgignore() and not ignored()"

- Find text files that contain a string::

    hg files "set:grep(magic) and not binary()"

- Find C files in a non-standard encoding::

    hg files "set:**.c and not encoding('UTF-8')"

- Revert copies of large binary files::

    hg revert "set:copied() and binary() and size('>1M')"

- Revert files that were added to the working directory::

    hg revert "set:revs('wdir()', added())"

- Remove files listed in foo.lst that contain the letter a or b::

    hg remove "set: listfile:foo.lst and (**a* or **b*)"