[rubygems/rubygems] Feature: accept pull request URLs as github source

Very often github source is used to temporarily use a modified gem
while a PR upstream is being reviewed.

So for instance https://github.com/ruby/bigdecimal/pull/211 will look like:

```ruby
gem "bigdecimal", github: "casperisfine/bigdecimal", branch: "git-gem" # https://github.com/ruby/bigdecimal/pull/200
```

It's annoying because you have to fiddle with the branch name, which is copied as `casperisfine:git-gem`, etc etc.

If I could simply use the PR URL like this:

```
gem "bigdecimal", github: "https://github.com/ruby/bigdecimal/pull/211"
```

It would make a very common task for me so much simpler.

https://github.com/rubygems/rubygems/commit/517c527751

1 files changed, 39 insertions, 0 deletions

diff --git a/spec/bundler/bundler/dsl_spec.rb b/spec/bundler/bundler/dsl_spec.rb
index 4d14949c89..a44a12924c 100644
--- a/spec/bundler/bundler/dsl_spec.rb
+++ b/spec/bundler/bundler/dsl_spec.rb
@@ -25,6 +25,45 @@ RSpec.describe Bundler::Dsl do
       expect { subject.git_source(:example) }.to raise_error(Bundler::InvalidOption)
     end
 
+    it "converts :github PR to URI using https" do
+      subject.gem("sparks", :github => "https://github.com/indirect/sparks/pull/5")
+      github_uri = "https://github.com/indirect/sparks.git"
+      expect(subject.dependencies.first.source.uri).to eq(github_uri)
+      expect(subject.dependencies.first.source.branch).to eq("refs/pull/5/head")
+    end
+
+    it "rejects :github PR URI with a branch, ref or tag" do
+      expect do
+        subject.gem("sparks", :github => "https://github.com/indirect/sparks/pull/5", :branch => "foo")
+      end.to raise_error(
+        Bundler::GemfileError,
+        %(The :branch option can't be used with `github: "https://github.com/indirect/sparks/pull/5"`),
+      )
+
+      expect do
+        subject.gem("sparks", :github => "https://github.com/indirect/sparks/pull/5", :ref => "foo")
+      end.to raise_error(
+        Bundler::GemfileError,
+        %(The :ref option can't be used with `github: "https://github.com/indirect/sparks/pull/5"`),
+      )
+
+      expect do
+        subject.gem("sparks", :github => "https://github.com/indirect/sparks/pull/5", :tag => "foo")
+      end.to raise_error(
+        Bundler::GemfileError,
+        %(The :tag option can't be used with `github: "https://github.com/indirect/sparks/pull/5"`),
+      )
+    end
+
+    it "rejects :github with :git" do
+      expect do
+        subject.gem("sparks", :github => "indirect/sparks", :git => "https://github.com/indirect/sparks.git")
+      end.to raise_error(
+        Bundler::GemfileError,
+        %(The :git option can't be used with `github: "indirect/sparks"`),
+      )
+    end
+
     context "default hosts", :bundler => "< 3" do
       it "converts :github to URI using https" do
         subject.gem("sparks", :github => "indirect/sparks")