diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index cfba2222..80b20508 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -17,7 +17,7 @@ To add support for a new extension:
 In addition, if this extension is already listed in [`languages.yml`][languages] then sometimes a few more steps will need to be taken:
 
 0. Make sure that example `.yourextension` files are present in the [samples directory][samples] for each language that uses `.yourextension`.
-0. Test the performance of the Bayesian classifier with a relatively large number (1000s) of sample `.yourextension` files. (ping @arfon or @bkeepers to help with this) to ensure we're not misclassifying files.
+0. Test the performance of the Bayesian classifier with a relatively large number (1000s) of sample `.yourextension` files. (ping **@arfon** or **@bkeepers** to help with this) to ensure we're not misclassifying files.
 0. If the Bayesian classifier does a bad job with the sample `.yourextension` files then a [heuristic](https://github.com/github/linguist/blob/master/lib/linguist/heuristics.rb) may need to be written to help.
 
 
@@ -28,10 +28,7 @@ We try only to add languages once they have some usage on GitHub. In most cases
 To add support for a new language:
 
 0. Add an entry for your language to [`languages.yml`][languages]. Omit the `language_id` field for now.
-0. Add a grammar for your language. Please only add grammars that have [one of these licenses](https://github.com/github/linguist/blob/257425141d4e2a5232786bf0b13c901ada075f93/vendor/licenses/config.yml#L2-L11).
-  0. Add your grammar as a submodule: `git submodule add https://github.com/JaneSmith/MyGrammar vendor/grammars/MyGrammar`.
-  0. Add your grammar to [`grammars.yml`][grammars] by running `script/convert-grammars --add vendor/grammars/MyGrammar`.
-  0. Download the license for the grammar: `script/licensed`. Be careful to only commit the file for the new grammar, as this script may update licenses for other grammars as well.
+0. Add a grammar for your language: `script/add-grammar https://github.com/JaneSmith/MyGrammar`. Please only add grammars that have [one of these licenses][licenses].
 0. Add samples for your language to the [samples directory][samples] in the correct subdirectory.
 0. Add a `language_id` for your language using `script/set-language-ids`. **You should only ever need to run `script/set-language-ids --update`. Anything other than this risks breaking GitHub search :cry:**
 0. Open a pull request, linking to a [GitHub search result](https://github.com/search?utf8=%E2%9C%93&q=extension%3Aboot+NOT+nothack&type=Code&ref=searchresults) showing in-the-wild usage.
@@ -39,7 +36,7 @@ To add support for a new language:
 In addition, if your new language defines an extension that's already listed in [`languages.yml`][languages] (such as `.foo`) then sometimes a few more steps will need to be taken:
 
 0. Make sure that example `.foo` files are present in the [samples directory][samples] for each language that uses `.foo`.
-0. Test the performance of the Bayesian classifier with a relatively large number (1000s) of sample `.foo` files. (ping @arfon or @bkeepers to help with this) to ensure we're not misclassifying files.
+0. Test the performance of the Bayesian classifier with a relatively large number (1000s) of sample `.foo` files. (ping **@arfon** or **@bkeepers** to help with this) to ensure we're not misclassifying files.
 0. If the Bayesian classifier does a bad job with the sample `.foo` files then a [heuristic](https://github.com/github/linguist/blob/master/lib/linguist/heuristics.rb) may need to be written to help.
 
 Remember, the goal here is to try and avoid false positives!
@@ -82,9 +79,9 @@ Here's our current build status: [![Build Status](https://api.travis-ci.org/gith
 
 Linguist is maintained with :heart: by:
 
-- @arfon (GitHub Staff)
-- @larsbrinkhoff
-- @pchaigno
+- **@arfon** (GitHub Staff)
+- **@larsbrinkhoff**
+- **@pchaigno**
 
 As Linguist is a production dependency for GitHub we have a couple of workflow restrictions:
 
@@ -113,5 +110,6 @@ If you are the current maintainer of this gem:
 
 [grammars]: /grammars.yml
 [languages]: /lib/linguist/languages.yml
+[licenses]: https://github.com/github/linguist/blob/257425141d4e2a5232786bf0b13c901ada075f93/vendor/licenses/config.yml#L2-L11
 [samples]: /samples
 [new-issue]: https://github.com/github/linguist/issues/new
diff --git a/script/add-grammar b/script/add-grammar
new file mode 100755
index 00000000..25c12176
--- /dev/null
+++ b/script/add-grammar
@@ -0,0 +1,93 @@
+#!/usr/bin/env ruby
+
+require "optparse"
+
+ROOT = File.expand_path("../../", __FILE__)
+
+
+# Break a repository URL into its separate components
+def parse_url(input)
+  hosts = "github\.com|bitbucket\.org|gitlab\.com"
+  
+  # HTTPS/HTTP link pointing to recognised hosts
+  if input =~ /^(?:https?:\/\/)?(?:[^.@]+@)?(?:www\.)?(#{hosts})\/([^\/]+)\/([^\/]+)/i
+    { host: $1.downcase(), user: $2, repo: $3.sub(/\.git$/, "") }
+  # SSH
+  elsif input =~ /^git@(#{hosts}):([^\/]+)\/([^\/]+)\.git$/i
+    { host: $1.downcase(), user: $2, repo: $3 }
+  # provider:user/repo
+  elsif input =~ /^(github|bitbucket|gitlab):\/?([^\/]+)\/([^\/]+)\/?$/i
+    { host: $1.downcase(), user: $2, repo: $3 }
+  # user/repo - Common GitHub shorthand
+  elsif input =~ /^\/?([^\/]+)\/([^\/]+)\/?$/
+    { host: "github.com", user: $1, repo: $2 }
+  else
+    raise "Unsupported URL: #{input}"
+  end
+end
+
+# Isolate the vendor-name component of a submodule path
+def parse_submodule(name)
+  name =~ /^(?:.*(?:vendor\/)?grammars\/)?([^\/]+)/i
+  path = "vendor/grammars/#{$1}"
+  unless File.exist?("#{ROOT}/" + path)
+    warn "Submodule '#{path}' does not exist. Aborting."
+    exit 1
+  end
+  path
+end
+
+# Print debugging feedback to STDOUT if running with --verbose
+def log(msg)
+  puts msg if $verbose
+end
+
+
+usage = """Usage:
+  #{$0} [-v|--verbose] [--replace grammar] url
+Examples:
+  #{$0} https://github.com/Alhadis/language-roff
+  #{$0} --replace sublime-apl https://github.com/Alhadis/language-apl
+"""
+
+$replace = nil
+$verbose = false
+
+OptionParser.new do |opts|
+  opts.banner = usage
+  opts.on("-v", "--verbose", "Print verbose feedback to STDOUT") do
+    $verbose = true
+  end
+  opts.on("-rSUBMODULE", "--replace=SUBMODDULE", "Replace an existing grammar submodule.") do |name|
+    $replace = name
+  end
+end.parse!
+
+
+$url = ARGV[0]
+
+# No URL? Print a usage message and bail.
+unless $url
+  warn usage
+  exit 1;
+end
+
+# Ensure the given URL is an HTTPS link
+parts    = parse_url $url
+https    = "https://#{parts[:host]}/#{parts[:user]}/#{parts[:repo]}"
+repo_new = "vendor/grammars/#{parts[:repo]}"
+repo_old = parse_submodule($replace) if $replace
+
+if repo_old
+  log "Deregistering: #{repo_old}"
+  `git submodule deinit #{repo_old}`
+  `git rm -rf #{repo_old}`
+end
+
+log "Registering new submodule: #{repo_new}"
+`git submodule add -f #{https} #{repo_new}`
+exit 1 if $?.exitstatus > 0
+`script/convert-grammars --add #{repo_new}`
+
+log "Confirming license"
+`script/licensed --module "#{repo_new}"`
diff --git a/script/licensed b/script/licensed
index ea3f538f..68214d34 100755
--- a/script/licensed
+++ b/script/licensed
@@ -4,6 +4,7 @@
 
 require "bundler/setup"
 require "licensed/cli"
+require "optparse"
 
 module Licensed
   module Source
@@ -32,7 +33,14 @@ module Licensed
   end
 end
 
-source = Licensed::Source::Filesystem.new("vendor/grammars/*/", type: "grammar")
+module_path = nil
+OptionParser.new do |opts|
+  opts.on("-mPATH", "--module=PATH", "Cache license file for specific grammar") do |p|
+    module_path = p
+  end
+end.parse!
+
+source = Licensed::Source::Filesystem.new(module_path || "vendor/grammars/*/", type: "grammar")
 config = Licensed::Configuration.new
 config.sources << source
 
@@ -43,4 +51,5 @@ else
 end
 
 command.run
+`git checkout -- vendor/licenses/grammar/` if module_path
 exit command.success?