From 816189f5be68c364d3beda4c20ed07d375f9f162 Mon Sep 17 00:00:00 2001
From: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Date: Sun, 25 Jul 2010 17:53:11 +0200
Subject: [PATCH] Atomic merges

Move the tree-merging method to Tree, and make it atomic: if merging
fails, the tree is not updated. Since the error propagates up, and the
tree merge is the first step of a commit merge, commit merges are atomic
too.
---
 rcs-fast-export.rb | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/rcs-fast-export.rb b/rcs-fast-export.rb
index 406ae45..45389f8 100755
--- a/rcs-fast-export.rb
+++ b/rcs-fast-export.rb
@@ -489,9 +489,17 @@ module RCS
 			@files = Hash.new
 		end
 
-		def add(rcs, rev)
-			if @files.key? rcs
-				prev = @files[rcs]
+		def merge!(tree)
+			testfiles = @files.dup
+			tree.each { |rcs, rev| self.add(rcs, rev, testfiles) }
+			# the next line is only reached if all the adds were
+			# succesfull, so the merge is atomic
+			@files.replace testfiles
+		end
+
+		def add(rcs, rev, file_list=@files)
+			if file_list.key? rcs
+				prev = file_list[rcs]
 				if prev.log == rev.log
 					str = "re-adding existing file #{rcs.fname} (old: #{prev.rev}, new: #{rev.rev})"
 				else
@@ -503,7 +511,7 @@ module RCS
 					@commit.warn_about str
 				end
 			end
-			@files[rcs] = rev
+			file_list[rcs] = rev
 		end
 
 		def each &block
@@ -557,9 +565,7 @@ module RCS
 		end
 
 		def merge!(commit)
-			commit.tree.each do |rcs, rev|
-				self.tree.add rcs, rev
-			end
+			self.tree.merge! commit.tree
 			if commit.date > self.date
 				warn_about "updating date to #{commit.date}"
 				self.date = commit.date
-- 
2.32.0.93.g670b81a890