annotate mercurial/help/filesets.txt @ 18792:10669e24eb6c

completion: add a debugpathcomplete command

The bash_completion code uses "hg status" to generate a list of
possible completions for commands that operate on files in the
working directory. In a large working directory, this can result
in a single tab-completion being very slow (several seconds) as a
result of checking the status of every file, even when there is no
need to check status or no possible matches.

The new debugpathcomplete command gains performance in a few simple
ways:

* Allow completion to operate on just a single directory. When used
  to complete the right commands, this considerably reduces the
  number of completions returned, at no loss in functionality.

* Never check the status of files. For completions that really must
  know if a file is modified, it is faster to use status:

  hg status -nm 'glob:myprefix**'

Performance:

Here are the commands used by bash_completion to complete, run in
the root of the mozilla-central working dir (~77,000 files) and
another repo (~165,000 files):

All "normal state" files (used by e.g. remove, revert):

                            mozilla    other
  status -nmcd 'glob:**'       1.77     4.10 sec
  debugpathcomplete -f -n      0.53     1.26
  debugpathcomplete -n         0.17     0.41

("-f" means "complete full paths", rather than the current directory)

Tracked files matching "a":

                            mozilla    other
  status -nmcd 'glob:a**'      0.26     0.47
  debugpathcomplete -f -n a    0.10     0.24
  debugpathcomplete -n a       0.10     0.22

We should be able to further improve completion performance once
the critbit work lands. Right now, our performance is limited by
the need to iterate over all keys in the dirstate.

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.

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'...'``.

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.

The following predicates are supported:

.. predicatesmarker

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 locate "set:grep(magic) and not binary()"

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

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

- Revert copies of large binary files::

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

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

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

See also :hg:`help patterns`.