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#3 in #licensing

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licensure

A software license header and copyright mangement tool.

Table of Contents

Why use Licensure?

According to the Apache Software Foundation: License headers allow someone examining the file to know the terms for the work, even when it is distributed without the rest of the distribution. Without a licensing notice, it must be assumed that the author has reserved all rights, including the right to copy, modify, and redistribute.

It's an easy extra step to make sure that no matter what file someone is looking at in your software they are aware of their rights and yours. However maintaining and updating a copyright notice in every source file can be a cumbersome exercise in patience. This is where Licensure comes in.

Licensure makes it easy to maintain and update your copyright notices across a project.

Installation

Install from Release (WIP)

  1. Navigate to the Releases Page
  2. Find the tar ball for your platform / architecture. For example, on 64 bit Mac OSX, the archive is named licensure_{version}_darwin_amd64.tar.gz
  3. Extract the tar ball
  4. Put the licensure binary in your $PATH

Install from Source

Licensure is available on crates.io and so can be installed with the following command:

cargo install licensure

Make sure that you have a working Rust environment. Instructions for setting one up can be found on the rustup website. You can then install licensure from source with the following commands:

git clone https://github.com/chasinglogic/licensure
cd licensure
cargo install --path .

If you need to update licensure via cargo you can then run the appropriate cargo install command with the --force flag.

Usage

Licensure searches for a config file .licensure.yml which will inform it's operation. Licensure will not function without a config file and if it cannot find one it will report this to you.

The method for finding a config file can be found in the Configuration section of this document. For our purposes we can generate a default config file with: licensure --generate-config. This will write an example configuration file with documentation comments into your current working directory. Note that the default config file this generates is not functional immediately as you must fill out the licenses section of the config. Licensure does not want to make assumptions about the licensing of your project.

In the following examples we will assume your using a simple configuration file such as the following:

licenses:
  - files: any
    ident: GPL-3.0
    authors:
      - name: Mathew Robinson
        email: chasinglogic@gmail.com
    auto_template: true
    
comments:
  - columns: 80
    extension: any
    commenter:
      type: line
      comment_char: "#"
      trailing_lines: 0

With this config file if you create a source file named test.py with the contents:

print("Hello world!")

We can then license this file with the command:

chasinglogic@galactica $ licensure test.py

Licensure will print out the licensed file as follows:

# Copyright 2018 Mathew Robinson <chasinglogic@gmail.com>. All rights reserved.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
print("Hello World!")

If we want to update the contents test.py instead of just printing out the licensed file content we can give Licensure the --in-place (or shortened form -i) flag:

chasinglogic@galactica $ licensure --in-place test.py

Licensure does some naive string comparison to determine if the header already exists. If you try to run licensure against a file which already has the generated license header it will skip it. You can see what files were skipped by running licensure with --verbose:

chasinglogic@galactica $ licensure --in-place --verbose test.py
test.py already licensed
chasinglogic@galactica $

This makes it safe and convenient to run licensure --in-place --project on the same project multiple times.

Configuration

Licensure requires the use of a configuration file. This section will explain all of the options of a configuration file, their definitions, and some explanation of how they work. If you're instead looking for the quickest way to get up and running you can generate a config with licensure --generate-config which will give you a default config file with documentation comments.

Where the Configuration File lives

The configuration file is written in yaml and is searched for by climbing the directory tree, starting at the current working directory, for a file named .licensure.yml. If it is not found the global configuration file located at $XDG_CONFIG_HOME/licensure/config.yml (where $XDG_CONFIG_HOME is $HOME/.config by default) will be used.

This essentially means that subdirectories can have their own licensure configs and the order of precedence is closest config file to the current working directory.

Top Level Configuration Options

The Configuration File only has a two top level options: exclude, and change_in_place. The other top level keys in the config file are referred to as Configuration Sections and make up the bulk of Licensure configuration.

change_in_place.

Takes a boolean indicating whether to change files in place when licensure is run. If this is set to false then when this config file is in use files will never be updated in place, even if --in-place is provided via the command line.

Example Configuration:

change_in_place: true

exclude

Takes a list of strings that will be compiled as regexes to filter out files from licensing. Excludes passed via the command line flag will be joined with any found in a config file.

Example Configuration:

# Regexes which if matched by a file path will always be excluded from
# getting a license header
excludes:
  - \.gitignore
  - .*lock
  - \.git/.*
  - \.licensure\.yml
  - README.*
  - LICENSE.*
  - .*\.(md|rst|txt)

Configuration Sections

Currently Licensure has two configuration sections: licenses and comments. They configure the two axes Licensure uses to generate a license header.

licenses

The licenses section is a list of license configuration objects. License configuration objects define what licenses should apply to what files, the templates for those licenses, and the copyright holders of those files. A license configuration object has the following form:

# Either a regex or the string "any" to determine to what files this
# license should apply. It is common for projects to have files
# under multiple licenses or with multiple copyright holders. This
# provides the ability to automatically license files correctly
# based on their file paths.
#
# If "any" is provided all files will match this license.
files: any

# The license identifier, a list of common identifiers can be
# found at: https://spdx.org/licenses/ but existence of the ident
# in this list it is not enforced unless auto_template is set to
# true.
ident: MIT

# A list of authors who hold copyright over these files
authors:
  # Provide either your full name or company name for copyright purposes
  - name: Your Name Here
    # Optionally provide email for copyright purposes
    # email: you@yourdomain.com

# The template that will be rendered to generate the header before
# comment characters are applied. Available variables are:
#  - [year]: substituted with the current year.
#  - [name of author]: Substituted with name of the author and email
#    if provided. If email is provided the output appears as Full
#    Name <email@example.com>. If multiple authors are provided the
#    list is concatenated together with commas.
template: |
  Copyright [year] [name of author]. All rights reserved. Use of
  this source code is governed by the [ident] license that can be
  found in the LICENSE file.

# If auto_template is true then the template configuration is ignored
# and the SPDX API will be queried with the ident value to
# automatically determine the license header template. auto_template
# works best with licenses that have a standardLicenseHeader field
# defined in their license info JSON, if it is not then we will use
# the full licenseText to generate the header which works fine for
# short licenses like MIT but can be quite lengthy for other licenses
# like BSD-4-Clause. The above default template is valid for most
# licenses and is recommended for MIT, and BSD licenses. Common
# licenses that work well with the auto_template feature are GPL
# variants, and the Apache 2.0 license.
#
# Important Note: this means the ident must be a valid SPDX identifier
# auto_template: true

A common licenses section would look like:

licenses:
  - files: any
    authors:
      - name: Mathew Robinson
        email: chasinglogic@gmail.com
        ident: MIT
    template: |
      Copyright [year] [name of author]. All rights reserved. Use of
      this source code is governed by the [ident] license that can be
      found in the LICENSE file.

comments

The comments section is a list of comment configuration objects. Comment configuration objects define how files with certain extensions will be commented. They can also define the column width to wrap the generated license header at. A comment configuration object has the following fields: extensions (or extension), columns, commenter,

Columns Configuration

The columns key specifies to what width the license header should be wrapped. Common values include: 80, 100, 120.

Example:

columns: 80
Extension Configuration

The extensions (or singular extension) field defines which file extensions to apply the commenter to. If extension is the string "any" then all extensions will match this comment configuration.

Example use of any:

extension: any

Example definition of explicit extensions

extensions:
  - js
  - rs
  - go
Commenter Configuration

The commenter field defines the kind of commenter to generate. There are two types of commenters: line and block.

A line commenter type will apply the comment_char to the beginning of each line in the license header. It will then add empty newlines to the end of the header equal to trailing_lines.

A block commenter type will add start_block_char as the first character in the license header and add end_block_char as the last character in the license header. When per_line_char is provided each line of the header between the block start and end characters will be line commented with the per_line_char.

If trailing_lines is omitted it's assumed to be 0.

Line Commenter Example

This is an example of a line commenter configuration.

commenter:
  type: line
  comment_char: "//"
  trailing_lines: 0

If this commenter is given the text:

A piece of text that
spans multiple lines

It would generate:

// A piece of text that 
// spans multiple lines

Note: when columns has a value the text may be re-wrapped to match the column width.

Block Commenter Example

This is an example of a block commenter configuration.

commenter:
  type: block
  start_block_char: "/*\n"
  end_block_char: "*/"
  per_line_char: "*"
  trailing_lines: 0

If this commenter is given the text:

A piece of text that
spans multiple lines

It would generate:

/*
* A piece of text that 
* spans multiple lines
*/

Note: when columns has a value the text may be re-wrapped to match the column width.

A Complete Configuration Example

The best up to date minimal example configuration is the one for licensure itself.

Contributing

  1. Fork it!
  2. Create your feature branch: git checkout -b my-new-feature
  3. Commit your changes: git commit -am 'Add some feature'
  4. Push to the branch: git push origin my-new-feature
  5. 🔥 Submit a pull request :D 🔥

License

This code is distributed under the GNU General Public License

    Copyright (C) 2019 Mathew Robinson

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

Dependencies

~10–23MB
~328K SLoC