sync_default_gems.rb: simplify rewriting commit message

Use "git commit --amend" instead of "git filter-branch" since we only
need to handle one commit at HEAD.

2 files changed, 24 insertions, 40 deletions

diff --git a/tool/sync_default_gems.rb b/tool/sync_default_gems.rb
index d927086d32..620539bcc9 100755
--- a/tool/sync_default_gems.rb
+++ b/tool/sync_default_gems.rb
@@ -415,18 +415,19 @@ module SyncDefaultGems
     Regexp.union(*patterns)
   end
 
-  def message_filter(repo, sha, input: ARGF)
+  def message_filter(repo, sha, log)
     unless repo.count("/") == 1 and /\A\S+\z/ =~ repo
       raise ArgumentError, "invalid repository: #{repo}"
     end
     unless /\A\h{10,40}\z/ =~ sha
       raise ArgumentError, "invalid commit-hash: #{sha}"
     end
-    log = input.read
-    log.delete!("\r")
-    log << "\n" if !log.end_with?("\n")
     repo_url = "https://github.com/#{repo}"
 
+    # Log messages generated by GitHub web UI have inconsistent line endings
+    log = log.delete("\r")
+    log << "\n" if !log.end_with?("\n")
+
     # Split the subject from the log message according to git conventions.
     # SPECIAL TREAT: when the first line ends with a dot `.` (which is not
     # obeying the conventions too), takes only that line.
@@ -457,7 +458,7 @@ module SyncDefaultGems
     else
       log = commit_url
     end
-    puts subject, "\n", log
+    "#{subject}\n\n#{log}"
   end
 
   def log_format(format, args, &block)
@@ -648,6 +649,21 @@ module SyncDefaultGems
       `git commit --amend --no-edit --all`
     end
 
+    # Update commit message to include links to the original commit
+    puts "Update commit message: #{sha}"
+    repo, = REPOSITORIES[gem]
+    headers, orig = IO.popen(%W[git cat-file commit #{sha}], "rb", &:read).split("\n\n", 2)
+    message = message_filter(repo, sha, orig)
+    IO.popen(%W[git commit --amend --no-edit -F -], "r+b") {|io|
+      io.write(message)
+      io.close_write
+      io.read
+    }
+    unless $?.success?
+      puts "Failed to modify commit message of #{sha}"
+      return nil
+    end
+
     return true
   end
 
@@ -684,32 +700,13 @@ module SyncDefaultGems
     puts "----"
 
     failed_commits = []
-
-    require 'shellwords'
-    filter = [
-      ENV.fetch('RUBY', 'ruby').shellescape,
-      File.realpath(__FILE__).shellescape,
-      "--message-filter",
-    ]
     commits.each do |sha, subject|
       puts "Pick #{sha} from #{repo}."
       case pickup_commit(gem, sha, edit)
       when false
-        next
+        # skipped
       when nil
         failed_commits << sha
-        next
-      end
-
-      puts "Update commit message: #{sha}"
-
-      # Run this script itself (tool/sync_default_gems.rb --message-filter) as a message filter
-      IO.popen({"FILTER_BRANCH_SQUELCH_WARNING" => "1"},
-               %W[git filter-branch -f --msg-filter #{[filter, repo, sha].join(' ')} -- HEAD~1..HEAD],
-               &:read)
-      unless $?.success?
-        puts "Failed to modify commit message of #{sha}"
-        break
       end
     end
 
@@ -799,13 +796,6 @@ module SyncDefaultGems
       next unless pattern =~ name or pattern =~ gem
       printf "%-15s https://github.com/%s\n", name, gem
     end
-  when "--message-filter"
-    ARGV.shift
-    if ARGV.size < 2
-      abort "usage: #{$0} --message-filter repository commit-hash [input...]"
-    end
-    message_filter(*ARGV.shift(2))
-    exit
   when "rdoc-ref"
     ARGV.shift
     pattern = ARGV.empty? ? %w[*.c *.rb *.rdoc] : ARGV
diff --git a/tool/test/test_sync_default_gems.rb b/tool/test/test_sync_default_gems.rb
index adbde66fbf..b0c9638862 100755
--- a/tool/test/test_sync_default_gems.rb
+++ b/tool/test/test_sync_default_gems.rb
@@ -19,14 +19,8 @@ module Test_SyncDefaultGems
         expected.concat(trailers.map {_1+"\n"})
       end
 
-      out, err = capture_output do
-        SyncDefaultGems.message_filter(repo, sha, input: StringIO.new(input, "r"))
-      end
-
-      all_assertions do |a|
-        a.for("error") {assert_empty err}
-        a.for("result") {assert_pattern_list(expected, out)}
-      end
+      out = SyncDefaultGems.message_filter(repo, sha, input)
+      assert_pattern_list(expected, out)
     end
 
     def test_subject_only