Common 'source' options.

Unless the part plugin overrides this behaviour, a part can use these
'source' keys in its definition. They tell snapcraft where to pull source
code for that part, and how to unpack it if necessary.

  - source: url-or-path

    A URL or path to some source tree to build. It can be local
    ('./src/foo') or remote ('https://foo.org/...'), and can refer to a
    directory tree or a tarball or a revision control repository
    ('git:...').

  - source-type: git, bzr, hg, svn, tar, deb, rpm, or zip

    In some cases the source string is not enough to identify the version
    control system or compression algorithm. The source-type key can tell
    snapcraft exactly how to treat that content.

  - source-depth: <integer>

    By default clones or branches with full history, specifying a depth
    will truncate the history to the specified number of commits.

  - source-branch: <branch-name>

    Snapcraft will checkout a specific branch from the source tree. This
    only works on multi-branch repositories from git and hg (mercurial).

  - source-commit: <commit>

    Snapcraft will checkout the specific commit from the source tree revision
    control system.

  - source-tag: <tag>

    Snapcraft will checkout the specific tag from the source tree revision
    control system.

  - source-subdir: path

    Snapcraft will checkout the repository or unpack the archive referred to
    by the 'source' keyword into parts/<part-name>/src/ but it will only
    copy the specified subdirectory into parts/<part-name>/build/

Note that plugins might well define their own semantics for the 'source'
keywords, because they handle specific build systems, and many languages
have their own built-in packaging systems (think CPAN, PyPI, NPM). In those
cases you want to refer to the help text for the specific plugin.

  snapcraft help <plugin>