mercurial/help/environment.txt

filemerge: make last line of prompts <40 english chars (issue6158)

I've chosen <40 as the target so that other languages that may have a 2x blowup
in character count can still have a chance to fit into an 80 column screen.

Previously, we would show a prompt like:

```
keep (l)ocal [dest], take (o)ther [source], or leave (u)nresolved for some/potentially/really/long/path?
```

On at least some systems, if readline was in use then the last line of the
prompt would be wrapped strangely if it couldn't fit entirely on one line. This
strange wrapping may be just a carriage return without a line feed, overwriting
the beginning of the line; example (100 columns wide, 65 character filename, and
yes there's 10 spaces on the end, I assume this is to handle the user inputting
longest word we provide as an option, "unresolved"):

```
ng/dir/name/that/does/not/work/well/with/readline/file.txt? ave (u)nresolved for some/lon
```

In some cases it may partially wrap onto the next line, but still be missing
earlier parts in the line, such as below (60 columns wide, 65 character
filename):

```
 rev], or leave (u)nresolved for some/long/dir/name/that/do
s/not/work/well/with/readline/file.txt?
```

With this fix, this looks like this on a 60 column screen:

```
tool vim_with_markers (for pattern some/long/dir/name/that/d
oes/not/work/well/with/readline/file.txt) can't handle binar
y
tool meld can't handle binary
tool vim_with_markers can't handle binary
tool internal:merge3 can't handle binary
tool merge can't handle binary
no tool found to merge some/long/dir/name/that/does/not/work
/well/with/readline/file.txt
file 'some/long/dir/name/that/does/not/work/well/with/readli
ne/file.txt' needs to be resolved.
You can keep (l)ocal [working copy], take (o)ther [merge rev
], or leave (u)nresolved.
What do you want to do?
```

Differential Revision: https://phab.mercurial-scm.org/D6562

HG
    Path to the 'hg' executable, automatically passed when running
    hooks, extensions or external tools. If unset or empty, this is
    the hg executable's name if it's frozen, or an executable named
    'hg' (with %PATHEXT% [defaulting to COM/EXE/BAT/CMD] extensions on
    Windows) is searched.

HGEDITOR
    This is the name of the editor to run when committing. See EDITOR.

    (deprecated, see :hg:`help config.ui.editor`)

HGENCODING
    This overrides the default locale setting detected by Mercurial.
    This setting is used to convert data including usernames,
    changeset descriptions, tag names, and branches. This setting can
    be overridden with the --encoding command-line option.

HGENCODINGMODE
    This sets Mercurial's behavior for handling unknown characters
    while transcoding user input. The default is "strict", which
    causes Mercurial to abort if it can't map a character. Other
    settings include "replace", which replaces unknown characters, and
    "ignore", which drops them. This setting can be overridden with
    the --encodingmode command-line option.

HGENCODINGAMBIGUOUS
    This sets Mercurial's behavior for handling characters with
    "ambiguous" widths like accented Latin characters with East Asian
    fonts. By default, Mercurial assumes ambiguous characters are
    narrow, set this variable to "wide" if such characters cause
    formatting problems.

HGMERGE
    An executable to use for resolving merge conflicts. The program
    will be executed with three arguments: local file, remote file,
    ancestor file.

    (deprecated, see :hg:`help config.ui.merge`)

HGRCPATH
    A list of files or directories to search for configuration
    files. Item separator is ":" on Unix, ";" on Windows. If HGRCPATH
    is not set, platform default search path is used. If empty, only
    the .hg/hgrc from the current repository is read.

    For each element in HGRCPATH:

    - if it's a directory, all files ending with .rc are added
    - otherwise, the file itself will be added

HGPLAIN
    When set, this disables any configuration settings that might
    change Mercurial's default output. This includes encoding,
    defaults, verbose mode, debug mode, quiet mode, tracebacks, and
    localization. This can be useful when scripting against Mercurial
    in the face of existing user configuration.

    In addition to the features disabled by ``HGPLAIN=``, the following
    values can be specified to adjust behavior:

    ``+strictflags``
        Restrict parsing of command line flags.

    Equivalent options set via command line flags or environment
    variables are not overridden.

    See :hg:`help scripting` for details.

HGPLAINEXCEPT
    This is a comma-separated list of features to preserve when
    HGPLAIN is enabled. Currently the following values are supported:

    ``alias``
        Don't remove aliases.
    ``color``
        Don't disable colored output.
    ``i18n``
        Preserve internationalization.
    ``revsetalias``
        Don't remove revset aliases.
    ``templatealias``
        Don't remove template aliases.
    ``progress``
        Don't hide progress output.

    Setting HGPLAINEXCEPT to anything (even an empty string) will
    enable plain mode.

HGUSER
    This is the string used as the author of a commit. If not set,
    available values will be considered in this order:

    - HGUSER (deprecated)
    - configuration files from the HGRCPATH
    - EMAIL
    - interactive prompt
    - LOGNAME (with ``@hostname`` appended)

    (deprecated, see :hg:`help config.ui.username`)

EMAIL
    May be used as the author of a commit; see HGUSER.

LOGNAME
    May be used as the author of a commit; see HGUSER.

VISUAL
    This is the name of the editor to use when committing. See EDITOR.

EDITOR
    Sometimes Mercurial needs to open a text file in an editor for a
    user to modify, for example when writing commit messages. The
    editor it uses is determined by looking at the environment
    variables HGEDITOR, VISUAL and EDITOR, in that order. The first
    non-empty one is chosen. If all of them are empty, the editor
    defaults to 'vi'.

PYTHONPATH
    This is used by Python to find imported modules and may need to be
    set appropriately if this Mercurial is not installed system-wide.