Add diff-driver command for semantic lockfile diffs and related tests

CHANGELOG.md

@@ -1,3 +1,7 @@
+## [Unreleased]
+
+- `git pkgs diff-driver` command for semantic lockfile diffs in `git diff`
+
 ## [0.3.0] - 2026-01-03
 
 - Pager support for long output (respects `GIT_PAGER`, `core.pager`, `PAGER`)

README.md

@@ -328,6 +328,30 @@ jobs:
       - run: git pkgs diff --from=origin/${{ github.base_ref }} --to=HEAD
 ```
 
+### Diff driver
+
+Install a git textconv driver that shows semantic dependency changes instead of raw lockfile diffs:
+
+```bash
+git pkgs diff-driver --install
+```
+
+Now `git diff` on lockfiles shows a sorted dependency list instead of raw lockfile changes:
+
+```diff
+diff --git a/Gemfile.lock b/Gemfile.lock
+--- a/Gemfile.lock
++++ b/Gemfile.lock
+@@ -1,3 +1,3 @@
++kamal 1.0.0
+-puma 5.0.0
++puma 6.0.0
+ rails 7.0.0
+-sidekiq 6.0.0
+```
+
+Use `git diff --no-textconv` to see the raw lockfile diff. To remove: `git pkgs diff-driver --uninstall`
+
 ## Configuration
 
 git-pkgs respects [standard git configuration](https://git-scm.com/docs/git-config).

lib/git/pkgs.rb

@@ -33,6 +33,7 @@
 require_relative "pkgs/commands/log"
 require_relative "pkgs/commands/upgrade"
 require_relative "pkgs/commands/schema"
+require_relative "pkgs/commands/diff_driver"
 
 module Git
   module Pkgs

lib/git/pkgs/cli.rb

@@ -5,7 +5,7 @@
 module Git
   module Pkgs
     class CLI
-      COMMANDS = %w[init update hooks info list tree history search why blame stale stats diff branch show log upgrade schema].freeze
+      COMMANDS = %w[init update hooks info list tree history search why blame stale stats diff branch show log upgrade schema diff-driver].freeze
       ALIASES = { "praise" => "blame", "outdated" => "stale" }.freeze
 
       def self.run(args)
@@ -36,7 +36,9 @@ def run
 
       def run_command(command)
         command = ALIASES.fetch(command, command)
-        command_class = Commands.const_get(command.capitalize.gsub(/_([a-z])/) { $1.upcase })
+        # Convert kebab-case or snake_case to PascalCase
+        class_name = command.split(/[-_]/).map(&:capitalize).join
+        command_class = Commands.const_get(class_name)
         command_class.new(@args).run
       rescue NameError
         $stderr.puts "Command '#{command}' not yet implemented"

lib/git/pkgs/commands/diff_driver.rb

@@ -0,0 +1,169 @@
+# frozen_string_literal: true
+
+require "bibliothecary"
+
+module Git
+  module Pkgs
+    module Commands
+      class DiffDriver
+        include Output
+
+        # Only lockfiles - manifests are human-readable and diff fine normally
+        LOCKFILE_PATTERNS = %w[
+          Brewfile.lock.json
+          Cargo.lock
+          Cartfile.resolved
+          Gemfile.lock
+          Gopkg.lock
+          Package.resolved
+          Pipfile.lock
+          Podfile.lock
+          Project.lock.json
+          bun.lock
+          composer.lock
+          gems.locked
+          glide.lock
+          go.sum
+          mix.lock
+          npm-shrinkwrap.json
+          package-lock.json
+          packages.lock.json
+          paket.lock
+          pnpm-lock.yaml
+          poetry.lock
+          project.assets.json
+          pubspec.lock
+          pylock.toml
+          shard.lock
+          uv.lock
+          yarn.lock
+        ].freeze
+
+        def initialize(args)
+          @args = args
+          @options = parse_options
+        end
+
+        def run
+          if @options[:install]
+            install_driver
+            return
+          end
+
+          if @options[:uninstall]
+            uninstall_driver
+            return
+          end
+
+          # textconv mode: single file argument, output dependency list
+          if @args.length == 1
+            output_textconv(@args[0])
+            return
+          end
+
+          error "Usage: git pkgs diff-driver <file>"
+        end
+
+        def output_textconv(file_path)
+          content = read_file(file_path)
+          deps = parse_deps(file_path, content)
+
+          # Output sorted dependency list for git to diff
+          deps.keys.sort.each do |name|
+            dep = deps[name]
+            # Only show type if it's not runtime (the default)
+            type_suffix = dep[:type] && dep[:type] != "runtime" ? " [#{dep[:type]}]" : ""
+            puts "#{name} #{dep[:requirement]}#{type_suffix}"
+          end
+        end
+
+        def install_driver
+          # Set up git config for textconv
+          system("git", "config", "diff.pkgs.textconv", "git-pkgs diff-driver")
+
+          # Add to .gitattributes
+          gitattributes_path = File.join(Dir.pwd, ".gitattributes")
+          existing = File.exist?(gitattributes_path) ? File.read(gitattributes_path) : ""
+
+          new_entries = []
+          LOCKFILE_PATTERNS.each do |pattern|
+            entry = "#{pattern} diff=pkgs"
+            new_entries << entry unless existing.include?(entry)
+          end
+
+          if new_entries.any?
+            File.open(gitattributes_path, "a") do |f|
+              f.puts unless existing.end_with?("\n") || existing.empty?
+              f.puts "# git-pkgs textconv for lockfiles"
+              new_entries.each { |entry| f.puts entry }
+            end
+          end
+
+          puts "Installed textconv driver for lockfiles."
+          puts "  git config: diff.pkgs.textconv = git-pkgs diff-driver"
+          puts "  .gitattributes: #{new_entries.count} lockfile patterns added"
+          puts
+          puts "Now 'git diff' on lockfiles shows dependency changes."
+          puts "Use 'git diff --no-textconv' to see raw diff."
+        end
+
+        def uninstall_driver
+          system("git", "config", "--unset", "diff.pkgs.textconv")
+
+          gitattributes_path = File.join(Dir.pwd, ".gitattributes")
+          if File.exist?(gitattributes_path)
+            lines = File.readlines(gitattributes_path)
+            lines.reject! { |line| line.include?("diff=pkgs") || line.include?("# git-pkgs") }
+            File.write(gitattributes_path, lines.join)
+          end
+
+          puts "Uninstalled diff driver."
+        end
+
+        def read_file(path)
+          return "" if path == "/dev/null"
+          return "" unless File.exist?(path)
+
+          File.read(path)
+        end
+
+        def parse_deps(path, content)
+          return {} if content.empty?
+
+          result = Bibliothecary.analyse_file(path, content).first
+          return {} unless result
+
+          result[:dependencies].map { |d| [d[:name], d] }.to_h
+        rescue StandardError
+          {}
+        end
+
+        def parse_options
+          options = {}
+
+          parser = OptionParser.new do |opts|
+            opts.banner = "Usage: git pkgs diff-driver <file>"
+            opts.separator ""
+            opts.separator "Outputs dependency list for git textconv diffing."
+
+            opts.on("--install", "Install textconv driver for lockfiles") do
+              options[:install] = true
+            end
+
+            opts.on("--uninstall", "Uninstall textconv driver") do
+              options[:uninstall] = true
+            end
+
+            opts.on("-h", "--help", "Show this help") do
+              puts opts
+              exit
+            end
+          end
+
+          parser.parse!(@args)
+          options
+        end
+      end
+    end
+  end
+end