NAME
    Path::IsDev - Determine if a given Path resembles a development source
    tree

VERSION
    version 1.001001

SYNOPSIS
        use Path::IsDev qw(is_dev);

        if( is_dev('/some/path') ) {
            ...
        } else {
            ...
        }

DESCRIPTION
    This module is more or less a bunch of heuristics for determining if a
    given path is a development tree root of some kind.

    This has many useful applications, notably ones that require behaviours
    for "installed" modules to be different to those that are still "in
    development"

FUNCTIONS
  debug
    Debug callback.

    To enable debugging:

        export PATH_ISDEV_DEBUG=1

  "is_dev"
    Using an "import"'ed "is_dev":

        if( is_dev( $path ) ) {

        }

    Though the actual heuristics used will be based on how "import" was
    called.

    Additionally, you can call

        Path::IsDev::is_dev

    without "import"ing anything, and it will behave exactly the same as if
    you'd imported it using

        use Path::IsDev qw( is_dev );

    That is, no "set" specification is applicable, so you'll only get the
    "default".

UNDERSTANDING AND DEBUGGING THIS MODULE
    Understanding how this module works, is critical to understand where you
    can use it, and the consequences of using it.

    This module operates on a very simplistic level, and its easy for
    false-positives to occur.

    There are two types of Heuristics, Postive/Confirming Heuristics, and
    Negative/Disconfirming Heuristics.

    Positive Heuristics and Negative Heuristics are based solely on the
    presence of specific marker files in a directory, or special marker
    directories.

    For instance, the files "META.yml", "Makefile.PL", and "Build.PL" are
    all Positive Heuristic markers, because their presence often indicates a
    "root" of a development tree.

    And for instance, the directories "t/", "xt/" and ".git/" are also
    Positive Heuristic markers, because these structures are common in
    "perl" development trees, and uncommon in install trees.

    However, these markers sometimes go wrong, for instance, consider you
    have a "local::lib" or "perlbrew" install in $HOME

        $HOME/
        $HOME/lib/
        $HOME/perl5/perls/perl-5.19.3/lib/site_perl/

    Etc.

    Under normal circumstances, neither $HOME nor those 3 paths are
    considered "dev".

    However, all it takes to cause a false positive, is for somebody to
    install a "t" or "xt" directory, or a marker file in one of the above
    directories for "path_isdev($dir)" to return true.

    This may not be a problem, at least, until you use "Path::FindDev" which
    combines "Path::IsDev" with recursive up-level traversal.

        $HOME/
        $HOME/lib/
        $HOME/perl5/perls/perl-5.19.3/lib/site_perl/

        find_dev('$HOME/perl5/perls/perl-5.19.3/lib/site_perl/') # returns false, because it is not inside a dev directory

        mkdir $HOME/t

        find_dev('$HOME/perl5/perls/perl-5.19.3/lib/site_perl/') # returns $HOME, because $HOME/t exists.

    And it is this kind of problem that usually catches people off guard.

        PATH_ISDEV_DEBUG=1 \
            perl -Ilib -MPath::FindDev=find_dev \
            -E "say find_dev(q{/home/kent/perl5/perlbrew/perls/perl-5.19.3/lib/site_perl})"

        ...
        [Path::IsDev=0] + ::Tool::Dzil => 0 : dist.ini does not exist
        [Path::IsDev=0] + ::Tool::MakeMaker => 0 : Makefile.PL does not exist
        [Path::IsDev=0] + ::Tool::ModuleBuild => 0 : Build.PL does not exist
        [Path::IsDev=0] + ::META => 0 : META.json does not exist
        [Path::IsDev=0] + ::META => 1 : META.yml exists
        [Path::IsDev=0] + ::META => 1 : /home/kent/perl5/META.yml is a file
        [Path::IsDev=0] + ::META matched path /home/kent/perl5
        /home/kent/perl5

    Whoops!.

        [Path::IsDev=0] + ::META => 1 : META.yml exists
        [Path::IsDev=0] + ::META => 1 : /home/kent/perl5/META.yml is a file

    No wonder!

        rm /home/kent/perl5/META.yml

        PATH_ISDEV_DEBUG=1 \
            perl -Ilib -MPath::FindDev=find_dev \
            -E "say find_dev(q{/home/kent/perl5/perlbrew/perls/perl-5.19.3/lib/site_perl})"

        ...
        [Path::IsDev=0] Matching /home/kent/perl5
        ...
        [Path::IsDev=0] + ::TestDir => 0 : xt does not exist
        [Path::IsDev=0] + ::TestDir => 1 : t exists
        [Path::IsDev=0] + ::TestDir => 1 : /home/kent/perl5/t is a dir
        [Path::IsDev=0] + ::TestDir matched path /home/kent/perl5
        /home/kent/perl5

    Double whoops!

        [Path::IsDev=0] + ::TestDir => 1 : t exists
        [Path::IsDev=0] + ::TestDir => 1 : /home/kent/perl5/t is a dir

    And you could keep doing that until you rule out all the bad heuristics
    in your tree.

    Or, you could use a negative heuristic.

        touch /home/kent/perl5/.path_isdev_ignore

        PATH_ISDEV_DEBUG=1 \
            perl -Ilib -MPath::FindDev=find_dev \
            -E "say find_dev(q{/home/kent/perl5/perlbrew/perls/perl-5.19.3/lib/site_perl})"
        ...
        [Path::IsDev=0] Matching /home/kent/perl5
        [Path::IsDev=0] - ::IsDev::IgnoreFile => 1 : .path_isdev_ignore exists
        [Path::IsDev=0] - ::IsDev::IgnoreFile => 1 : /home/kent/perl5/.path_isdev_ignore is a file
        [Path::IsDev=0] - ::IsDev::IgnoreFile excludes path /home/kent/perl5
        [Path::IsDev=0] no match found
        ...
        [Path::IsDev=0] Matching /
        ...
        [Path::IsDev=0] no match found

    Success!

        [Path::IsDev=0] - ::IsDev::IgnoreFile => 1 : .path_isdev_ignore exists
        [Path::IsDev=0] - ::IsDev::IgnoreFile => 1 : /home/kent/perl5/.path_isdev_ignore is a file

HEURISTICS
  Negative Heuristics bundled with this distribution
    Just remember, a Negative Heuristic excludes the path it is associated
    with

    *   "IsDev::IgnoreFile" - ".path_isdev_ignore"

  Positive Heuristics bundled with this distribution
    *   "Changelog" - Files matching "Changes", "Changelog", and similar,
        case insensitive, extensions optional.

    *   "DevDirMarker" - explicit ".devdir" file to indicate a project root.

    *   "META" - "META.yml"/"META.json"

    *   "MYMETA" - "MYMETA.yml"/"MYMETA.json"

    *   "Makefile" - Any "Makefile" format documented supported by GNU Make

    *   "TestDir" - A directory called either "t/" or "xt/"

    *   "Tool::DZil" - A "dist.ini" file

    *   "Tool::MakeMaker" - A "Makefile.PL" file

    *   "Tool::ModuleBuild" - A "Build.PL" file

    *   "VCS::Git" - A ".git" directory

HEURISTIC SETS
  Heuristic Sets Bundled with this distribution
    *   "Basic" - The basic heuristic set that contains most, if not all
        heuristics.

ADVANCED USAGE
  Custom Sets
    "Path::IsDev" has a system of "sets" of Heuristics, in order to allow
    for pluggable and flexible heuristic types.

    Though, for the vast majority of cases, this is not required.

        use Path::IsDev is_dev => { set => 'Basic' };
        use Path::IsDev is_dev => { set => 'SomeOtherSet' , -as => 'is_dev_other' };

  Overriding the default set
    If for whatever reason the "Basic" set is insufficient, or if it false
    positives on your system for some reason, the "default" set can be
    overridden.

        export PATH_ISDEV_DEFAULT_SET="SomeOtherSet"

        ...
        use Path::IsDev qw( is_dev );
        is_dev('/some/path') # uses SomeOtherSet

    Though this will only take priority in the event the set is not
    specified during "import"

    If this poses a security concern for the user, then this security hole
    can be eliminated by declaring the set you want in code:

        export PATH_ISDEV_DEFAULT_SET="SomeOtherSet"

        ...
        use Path::IsDev  is_dev => { set => 'Basic' };
        is_dev('/some/path') # uses Basic, regardless of ENV

SECURITY
    Its conceivable, than an evil user could construct an evil set,
    containing arbitrary and vulnerable code, and possibly stash that evil
    set in a poorly secured privileged users @INC

    And if they managed to achieve that, if they could poison the privileged
    users %ENV, they could trick the privileged user into executing
    arbitrary code.

    Though granted, if you can do either of those 2 things, you're probably
    security vulnerable anyway, and granted, if you could do either of those
    2 things you could do much more evil things by the following:

        export PERL5OPT="-MEvil::Module"

    So with that in understanding, saying this modules default utility is
    "insecure" is mostly a bogus argument.

    And to that effect, this module does nothing to "lock down" that
    mechanism, and this module encourages you to NOT force a set, unless you
    NEED to, and strongly suggests that forcing a set for the purpose of
    security will achieve no real improvement in security, while
    simultaneously reducing utility.

AUTHOR
    Kent Fredric <kentfredric@gmail.com>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2014 by Kent Fredric
    <kentfredric@gmail.com>.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

