gemdiff is a command-line tool to find source code for ruby gems. It connects gem version management (rubygems + bundler) with source code (GitHub).

gemdiff provides commands to

• Find GitHub repositories for gems
• Open the compare view for two gem versions
• Inspect your bundle and list all the available updates
• Simplify your git workflow for updating gems

You want to view differences between versions of gems before updating. gemdiff does the source repository lookup, opens a compare view of commits on GitHub, and simplifies your git workflow for a bundled project.

gemdiff finds a repository by inspecting the local or remote gemspec, or searching GitHub if needed. It uses bundler to list your outdated gems. For each outdated gem, it determines your currently used version and the version you can update to, and builds a compare view URL with the old and new version tags.

Run gemdiff update [gem] to update a gem (bundle update [gem]) and commit the change with a nice commit message that includes the old and new versions and a compare URL with the changes.

gem install gemdiff

Runs bundle outdated --strict in the current directory. Outputs outdated gems in your bundle with their compare URLs to stdout. list is the default command.

$ cd /your/ruby/project/using/bundler
$ gemdiff
Checking for outdated gems in your bundle...
Fetching gem metadata from https://rubygems.org/.......
Fetching version metadata from https://rubygems.org/..
Resolving dependencies...

Outdated gems included in the bundle:
  * mocha (newest 1.2.1, installed 1.1.0, requested ~> 1.0) in group "development"
  * rake (newest 11.3.0, installed 11.1.2, requested ~> 11.0) in group "development"
  * sqlite3 (newest 1.3.12, installed 1.3.11, requested ~> 1.3) in group "development"

mocha: 1.2.1 > 1.1.0
https://github.com/freerange/mocha/compare/v1.1.0...v1.2.1

rake: 11.3.0 > 11.1.2
https://github.com/ruby/rake/compare/v11.1.2...v11.3.0

sqlite3: 1.3.12 > 1.3.11
https://github.com/sparklemotion/sqlite3-ruby/compare/v1.3.11...v1.3.12

Runs bundle outdated --strict in the current directory. For each outdated gem, you can open the compare view for that gem, skip it, or exit. Enter y to review. Enter A to open all compare views (beware!). Enter s to list all the compare URLs to stdout (same as the list command).

$ gemdiff each
Checking for outdated gems in your bundle...
Fetching gem metadata from https://rubygems.org/.......
Fetching version metadata from https://rubygems.org/..
Resolving dependencies...

Outdated gems included in the bundle:
  * aws-sdk (1.35.0 > 1.34.1)
  * sprockets (2.11.0 > 2.10.1)
  * webmock (1.17.4 > 1.17.3)
aws-sdk: 1.35.0 > 1.34.1
Open? (y to open, x to exit, A to open all, s to show all to stdout, else skip)
sprockets: 2.11.0 > 2.10.1
Open? (y to open, x to exit, A to open all, s to show all to stdout, else skip) y
webmock: 1.17.4 > 1.17.3
Open? (y to open, x to exit, A to open all, s to show all to stdout, else skip)

Update a gem in your bundle and commit the change with git. A compare URL showing the difference between the versions will be part of the commit message. You will be shown a preview of the git diff and you may choose to commit or reset the change.

$ gemdiff update nokogiri

Updating nokogiri...
diff --git a/Gemfile.lock b/Gemfile.lock
index b074472..e0554f2 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -102,7 +102,7 @@ GEM
     mini_portile2 (2.1.0)
     minitest (5.10.1)
     nio4r (2.0.0)
-    nokogiri (1.7.1)
+    nokogiri (1.7.2)
       mini_portile2 (~> 2.1.0)
     orm_adapter (0.5.0)
     parser (2.4.0.0)

Commit? (c to commit, r to reset, else do nothing) c

commit 1131db6f57ccad8ed3dab6759c6b1306f98a165c
Author: Tee Parham
Date:   Fri May 12 14:04:26 2017 -0600

    Update nokogiri to 1.7.2

    https://github.com/sparklemotion/nokogiri/compare/v1.7.1...v1.7.2

diff --git a/Gemfile.lock b/Gemfile.lock
...

Show the repository URL using the gemspec. If a GitHub URL is not found, query the GitHub search API.

$ gemdiff find pundit
https://github.com/varvet/pundit

Open the repository URL with your default browser (or whatever your operating system is configured to run with the open command with a URL argument):

$ gemdiff open pundit

You may also use . as a shortcut for the current directory name. This is helpful if you would like to quickly open the gem you are developing, for example:

$ pwd
/Users/you/projects/somegem
$ gemdiff open .

Open a compare view for an individual outdated gem in your bundle:

$ gemdiff compare pundit

You can bypass bundler and query a gem by including the old and new version numbers. This is faster since it bypasses the bundle outdated --strict command used to get the versions.

For example, open the GitHub compare view in browser for difference between pundit versions 0.3.0 and 1.0.0:

$ gemdiff compare pundit 1.0.0 0.3.0

You can compare a version with a branch name:

$ gemdiff compare arel 6.0.0 main

Open the repository's release history page:

$ gemdiff releases haml

Open the repository's main branch commit history page:

$ gemdiff main haml

To get help on the command line:

$ gemdiff help

You can use abbreviations for any of the above commands. For example, this is equivalent to gemdiff find pundit:

$ gemdiff f pundit
https://github.com/varvet/pundit

All commands that have a gem name argument can now use "." as an alias for the current directory name.

For example:

pwd
/Users/you/ruby/somegem
gemdiff find .
gemdiff open .
gemdiff main .
gemdiff compare . 1.2.3 main

If GitHub returns rate limit errors, you can make authenticated API requests to GitHub. Set the GEMDIFF_GITHUB_TOKEN or GITHUB_TOKEN environment variable to a personal access token. Using GEMDIFF_GITHUB_TOKEN is recommended, since other programs such as hub use GITHUB_TOKEN.

gemdiff assumes a few things:

1. The gem must have a repository on GitHub. If not, gemdiff will find nothing or a similar repository, which is not helpful. Some gems' source code is not on GitHub. gemdiff could support other source hosts. Submit a pull request!

2. The GitHub repository must have tagged releases to show compare views. If you find gems that do not tag releases, submit an issue to the gem maintainer to tag their releases.

3. The versions must be tagged using the standard format of v1.2.3. If you find gems that follow a non-standard format (such as 1.2.3), please open an issue or submit a pull request. See lib/gemdiff/outdated_gem.rb.

4. Encourage gem maintainers to enter the GitHub repository URL in the homepage field of their gemspec or anywhere in the description. If you find exceptions, open an issue or submit a pull request. See lib/gemdiff/repo_finder.rb.

Slides from lightning talk at Boulder Ruby 4/15/2014