annotate mercurial/helptext/revisions.txt @ 47120:7109a38830c9

dirstate-tree: Fold "tracked descendants" counter update in main walk

For the purpose of implementing `has_tracked_dir` (which means "has tracked
descendants) without an expensive sub-tree traversal, we maintaing a counter
of tracked descendants on each "directory" node of the tree-shaped dirstate.

Before this changeset, mutating or inserting a node at a given path would
involve:

* Walking the tree from root through ancestors to find the node or the spot
  where to insert it
* Looking at the previous node if any to decide what counter update is needed
* Performing any node mutation
* Walking the tree *again* to update counters in ancestor nodes

When profiling `hg status` on a large repo, this second walk takes times
while loading a the dirstate from disk.

It turns out we have enough information to decide before he first tree walk
what counter update is needed. This changeset merges the two walks, gaining
~10% of the total time for `hg update` (in the same hyperfine benchmark as
the previous changeset).

---

Profiling was done by compiling with this `.cargo/config`:

    [profile.release]
    debug = true

then running with:

    py-spy record -r 500 -n -o /tmp/hg.json --format speedscope -- \
    ./hg status -R $REPO --config experimental.dirstate-tree.in-memory=1

then visualizing the recorded JSON file in https://www.speedscope.app/

Differential Revision: https://phab.mercurial-scm.org/D10554

Mercurial supports several ways to specify revisions.

Specifying single revisions
===========================

A plain integer is treated as a revision number. Negative integers are
treated as sequential offsets from the tip, with -1 denoting the tip,
-2 denoting the revision prior to the tip, and so forth.

A 40-digit hexadecimal string is treated as a unique revision identifier.
A hexadecimal string less than 40 characters long is treated as a
unique revision identifier and is referred to as a short-form
identifier. A short-form identifier is only valid if it is the prefix
of exactly one full-length identifier.

Any other string is treated as a bookmark, tag, or branch name. A
bookmark is a movable pointer to a revision. A tag is a permanent name
associated with a revision. A branch name denotes the tipmost open branch head
of that branch - or if they are all closed, the tipmost closed head of the
branch. Bookmark, tag, and branch names must not contain the ":" character.

The reserved name "tip" always identifies the most recent revision.

The reserved name "null" indicates the null revision. This is the
revision of an empty repository, and the parent of revision 0.

The reserved name "." indicates the working directory parent. If no
working directory is checked out, it is equivalent to null. If an
uncommitted merge is in progress, "." is the revision of the first
parent.

Finally, commands that expect a single revision (like ``hg update``) also
accept revsets (see below for details). When given a revset, they use the
last revision of the revset. A few commands accept two single revisions
(like ``hg diff``). When given a revset, they use the first and the last
revisions of the revset.

Specifying multiple revisions
=============================

Mercurial supports a functional language for selecting a set of
revisions. Expressions in this language are called revsets.

The language supports a number of predicates which are joined by infix
operators. Parenthesis can be used for grouping.

Identifiers such as branch names may need quoting with single or
double quotes if they contain characters like ``-`` or if they match
one of the predefined 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'...'``.

Operators
=========

There is a single prefix operator:

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

These are the supported infix operators:

``x::y``
  A DAG range, meaning all changesets that are descendants of x and
  ancestors of y, including x and y themselves. If the first endpoint
  is left out, this is equivalent to ``ancestors(y)``, if the second
  is left out it is equivalent to ``descendants(x)``.

  An alternative syntax is ``x..y``.

``x:y``
  All changesets with revision numbers between x and y, both
  inclusive. Either endpoint can be left out, they default to 0 and
  tip.

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

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

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

``x % y``
  Changesets that are ancestors of x but not ancestors of y (i.e. ::x - ::y).
  This is shorthand notation for ``only(x, y)`` (see below). The second
  argument is optional and, if left out, is equivalent to ``only(x)``.

``x^n``
  The nth parent of x, n == 0, 1, or 2.
  For n == 0, x; for n == 1, the first parent of each changeset in x;
  for n == 2, the second parent of changeset in x.

``x~n``
  The nth first ancestor of x; ``x~0`` is x; ``x~3`` is ``x^^^``.
  For n < 0, the nth unambiguous descendent of x.

``x ## y``
  Concatenate strings and identifiers into one string.

  All other prefix, infix and postfix operators have lower priority than
  ``##``. For example, ``a1 ## a2~2`` is equivalent to ``(a1 ## a2)~2``.

  For example::

    [revsetalias]
    issue(a1) = grep(r'\bissue[ :]?' ## a1 ## r'\b|\bbug\(' ## a1 ## r'\)')

  ``issue(1234)`` is equivalent to
  ``grep(r'\bissue[ :]?1234\b|\bbug\(1234\)')``
  in this case. This matches against all of "issue 1234", "issue:1234",
  "issue1234" and "bug(1234)".

There is a single postfix operator:

``x^``
  Equivalent to ``x^1``, the first parent of each changeset in x.

Patterns
========

Where noted, predicates that perform string matching can accept a pattern
string. The pattern may be either a literal, or a regular expression. If the
pattern starts with ``re:``, the remainder of the pattern is treated as a
regular expression. Otherwise, it is treated as a literal. To match a pattern
that actually starts with ``re:``, use the prefix ``literal:``.

Matching is case-sensitive, unless otherwise noted.  To perform a case-
insensitive match on a case-sensitive predicate, use a regular expression,
prefixed with ``(?i)``.

For example, ``tag(r're:(?i)release')`` matches "release" or "RELEASE"
or "Release", etc.

Predicates
==========

The following predicates are supported:

.. predicatesmarker

Aliases
=======

New predicates (known as "aliases") can be defined, using any combination of
existing predicates or other aliases. An alias definition looks like::

  <alias> = <definition>

in the ``revsetalias`` section of a Mercurial configuration file. Arguments
of the form `a1`, `a2`, etc. are substituted from the alias into the
definition.

For example,

::

  [revsetalias]
  h = heads()
  d(s) = sort(s, date)
  rs(s, k) = reverse(sort(s, k))

defines three aliases, ``h``, ``d``, and ``rs``. ``rs(0:tip, author)`` is
exactly equivalent to ``reverse(sort(0:tip, author))``.

Equivalents
===========

Command line equivalents for :hg:`log`::

  -f    ->  ::.
  -d x  ->  date(x)
  -k x  ->  keyword(x)
  -m    ->  merge()
  -u x  ->  user(x)
  -b x  ->  branch(x)
  -P x  ->  !::x
  -l x  ->  limit(expr, x)

Examples
========

Some sample queries:

- Changesets on the default branch::

    hg log -r "branch(default)"

- Changesets on the default branch since tag 1.5 (excluding merges)::

    hg log -r "branch(default) and 1.5:: and not merge()"

- Open branch heads::

    hg log -r "head() and not closed()"

- Changesets between tags 1.3 and 1.5 mentioning "bug" that affect
  ``hgext/*``::

    hg log -r "1.3::1.5 and keyword(bug) and file('hgext/*')"

- Changesets committed in May 2008, sorted by user::

    hg log -r "sort(date('May 2008'), user)"

- Changesets mentioning "bug" or "issue" that are not in a tagged
  release::

    hg log -r "(keyword(bug) or keyword(issue)) and not ancestors(tag())"

- Update to the commit that bookmark @ is pointing to, without activating the
  bookmark (this works because the last revision of the revset is used)::

    hg update :@

- Show diff between tags 1.3 and 1.5 (this works because the first and the
  last revisions of the revset are used)::

    hg diff -r 1.3::1.5