Fix dependency constraint on ruby-git

CHANGELOG.md

@@ -11,6 +11,8 @@
 ## master
 
 * Update Octokit dependency to version 6.0 - [@spencertransier](https://github.com/spencertransier) [#1437](https://github.com/danger/danger/pull/1437)
+<!-- Your comment above here -->
+* Fixes dependency constraint issue on `ruby-git` - [@ainame](https://github.com/ainame) [#1436](https://github.com/danger/danger/pull/1436)
 
 ## 9.3.0
 

danger.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency "cork", "~> 0.1"
   spec.add_runtime_dependency "faraday", ">= 0.9.0", "< 3.0"
   spec.add_runtime_dependency "faraday-http-cache", "~> 2.0"
-  spec.add_runtime_dependency "git", "~> 1.13.0"
+  spec.add_runtime_dependency "git", "~> 1.13"
   spec.add_runtime_dependency "kramdown", "~> 2.3"
   spec.add_runtime_dependency "kramdown-parser-gfm", "~> 1.0"
   spec.add_runtime_dependency "no_proxy_fix"

lib/danger/scm_source/git_repo.rb

@@ -8,13 +8,9 @@ class GitRepo
 
     def diff_for_folder(folder, from: "master", to: "HEAD", lookup_top_level: false)
       self.folder = folder
-      git_top_level = folder
-      if lookup_top_level
-        Dir.chdir(folder) do
-          git_top_level = exec("rev-parse --show-toplevel")
-        end
-      end
-      repo = Git.open git_top_level
+      git_top_level = find_git_top_level_if_needed!(folder, lookup_top_level)
+
+      repo = Git.open(git_top_level)
 
       ensure_commitish_exists!(from)
       ensure_commitish_exists!(to)
@@ -168,6 +164,26 @@ def commits_in_branch_count(from, to)
     def commit_is_ref?(commit)
       /[a-f0-9]{5,40}/ !~ commit
     end
+
+    def find_git_top_level_if_needed!(folder, lookup_top_level)
+      git_top_level = Dir.chdir(folder) { exec("rev-parse --show-toplevel") }
+      return git_top_level if lookup_top_level
+
+      # To keep backward compatibility, `GitRepo#diff_for_folder` expects folder
+      # to be top level git directory or requires `true` to `lookup_top_level`.
+      # https://github.com/danger/danger/pull/1178
+      return folder if compare_path(git_top_level, folder)
+
+      message = "#{folder} is not the top level git directory. Pass correct path or `true` to `lookup_top_level` option for `diff_for_folder`"
+      raise ArgumentError, message
+    end
+
+    # Compare given paths as realpath. Return true if both are same.
+    # `git rev-parse --show-toplevel` returns a path resolving symlink. In rspec, given path can
+    # be a temporary directory's path created under a symlinked directory `/var`.
+    def compare_path(path1, path2)
+      Pathname.new(path1).realdirpath == Pathname.new(path2).realdirpath
+    end
   end
 end
 

spec/lib/danger/scm_source/git_repo_spec.rb

@@ -43,14 +43,16 @@
         @dm = testing_dangerfile
         expect do
           @dm.env.scm.diff_for_folder(dir + "/subdir")
-        end.to raise_error(ArgumentError, /path does not exist/)
+        end.to raise_error(ArgumentError, /is not the top level git directory/)
       end
     end
 
     it "looks up the top level git folder when requested" do
       with_git_repo do |dir|
         @dm = testing_dangerfile
-        @dm.env.scm.diff_for_folder(dir + "/subdir", lookup_top_level: true)
+        expect do
+          @dm.env.scm.diff_for_folder(dir + "/subdir", lookup_top_level: true)
+        end.not_to raise_error
       end
     end
   end