[PATCH] Add git-graft-ripple, a tool for permanently grafting history into a tree.

[Ryan Anderson <ryan@michonline.com>]

Enhancements over the original example:

	o Each newly created commit A' references A, and (A^1)' (The first try
	referenced A^1 and (A^1)' but not A)

	o Support for incrementally rewriting history is present.

Signed-off-by: Ryan Anderson <ryan@michonline.com>

---

 Documentation/git-graft-ripple |   57 +++++++++++++++++
 Makefile                       |    3 +
 git-graft-ripple.perl          |  137 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 196 insertions(+), 1 deletions(-)
 create mode 100644 Documentation/git-graft-ripple
 create mode 100755 git-graft-ripple.perl

applies-to: 92551f12af8cd77f821d066a53c4dd301d1b41f5
9bfbdd948e6c0c9a8f0383b355e5cbbb42e0a772
diff --git a/Documentation/git-graft-ripple b/Documentation/git-graft-ripple
new file mode 100644
index 0000000..2fa38cb
--- /dev/null
+++ b/Documentation/git-graft-ripple
@@ -0,0 +1,57 @@
+git-graft-ripple(1)
+===============
+
+NAME
+----
+git-graft-ripple - Rewrite history with an additional commitish as a parent.
+
+
+SYNOPSIS
+--------
+'git-log <git repository> <branch committish> <graft SHA1> [start commitish]'
+
+DESCRIPTION
+-----------
+
+git-graft-ripple rewrites a series of commit objects by adding a new parent to
+the most ancestral commit, and passing the changed history back up through the
+revision history.
+
+Proceeding in reverse merge order a new commit is created using the following
+algorithim:
+
+	If this is the first commit reached, append the graft object name to
+	the parents.
+
+	Replace each parent object name with the object name generated by this
+	algorithm earlier.
+
+	Add the original object name to the parents.
+
+If a start commitish is given, the output of git-rev-list is restricted using
+it. This allows for incremental grafting to occur.
+
+Note: No branches are modified by this operation.
+
+Files
+-----
+
+GIT_DIR/info/ripple-status contains a mapping between the original object name
+and the object name generated by this algorithm. When doing incremental
+grafting, this file is necessary to continue to rename objects. If this is not
+present, git-graft-ripple will leave the old object name in the list of
+parents, which should still allow most merges to occur cleanly.
+
+
+Author
+------
+Written by Ryan Anderson <ryan@michonline.com>
+
+Documentation
+--------------
+Documentation by Ryan Anderson.
+
+GIT
+---
+Part of the gitlink:git[7] suite
+
diff --git a/Makefile b/Makefile
index 1109dc6..984be32 100644
--- a/Makefile
+++ b/Makefile
@@ -97,7 +97,8 @@ SCRIPT_SH = \
 SCRIPT_PERL = \
 	git-archimport.perl git-cvsimport.perl git-relink.perl \
 	git-shortlog.perl git-fmt-merge-msg.perl \
-	git-svnimport.perl git-mv.perl git-cvsexportcommit.perl
+	git-svnimport.perl git-mv.perl git-cvsexportcommit.perl \
+	git-graft-ripple.perl
 
 SCRIPT_PYTHON = \
 	git-merge-recursive.py
diff --git a/git-graft-ripple.perl b/git-graft-ripple.perl
new file mode 100755
index 0000000..b8ec990
--- /dev/null
+++ b/git-graft-ripple.perl
@@ -0,0 +1,137 @@
+#!/usr/bin/perl
+# Copyright 2005 Ryan Anderson <ryan@michonline.com>
+#
+# GPL v2 (See COPYING)
+#
+# This file is licensed under the GPL v2, or a later version
+# at the discretion of Linus Torvalds.
+
+use strict;
+use warnings;
+
+use IPC::Open2;
+
+sub git_commit_tree {
+        my ($tree,$comments,@parents) = @_;
+
+        my @cparents;
+        foreach my $p (@parents) {
+                push @cparents,"-p",$p;
+        }
+
+        my $pid = open2(*Reader, *Writer,
+		"git-commit-tree",$tree,@cparents);
+        print Writer $comments;
+        close(Writer);
+        my $commit = <Reader>;
+
+        waitpid $pid, 0;
+        close(Reader);
+
+        chomp $commit;
+
+        return $commit;
+}
+
+my ($gittree,$branch,$graft,$start) = @ARGV;
+chdir($gittree)
+	or die sprintf("Failed to chdir to '%s': %s\n", $ARGV[0], $!);
+
+my $range = defined $start ? sprintf("%s..%s",$start,$branch) : $branch;
+
+#printf("Running git-rev-list --parents --merge-order %s\n",$range);
+open(GRL,"-|","git-rev-list","--parents", "--merge-order", $range)
+	or die "Failed to run git-rev-list: " . $!;
+
+my %csets;
+my @revs;
+while(<GRL>) {
+	chomp;
+	my ($commit,@parents) = split;
+	$csets{$commit}{parents} = \@parents;
+	push @revs, $commit;
+#	printf("Investigating %s\n", $commit);
+
+	open(GCF,"-|","git-cat-file","commit",$commit)
+		or die "Failed to open git-cat-file: " . $!;
+
+	my $in_comments = 0;
+	while(<GCF>) {
+		chomp;
+		if ($in_comments) {
+			$csets{$commit}{comments} .= $_ . "\n";
+
+		} elsif (m/^tree (.+)$/) {
+			$csets{$commit}{tree} = $1;
+			#printf("tree = %s\n",$1);
+
+		} elsif (m/^parent (.+)$/) {
+			# Do nothing, we already got
+			# the parents from rev-list.
+
+		} elsif (m/^(author|committer) (.*) <(.*)> (.*)$/) {
+			#printf("%s = %s <%s> at %s\n",$1, $2,$3,$4);
+			@{$csets{$commit}{$1}}{qw(name email datetime)}
+				= ($2,$3,$4);
+
+		} elsif (length == 0) {
+			$in_comments = 1;
+			$csets{$commit}{comments} = "";
+			next;
+		}
+	}
+	close(GCF);
+
+}
+close(GRL);
+
+@revs = reverse @revs;
+shift @revs if defined $start;
+push @{$csets{$revs[0]}{parents}},$graft;
+
+my %newcsets;
+if (-f ".git/info/ripple-status") {
+	open(RSTATUS,"<",".git/info/ripple-status")
+		or die "Failed to restore status from .git/info/ripple-status: " . $!;
+
+	while (<RSTATUS>) {
+		chomp;
+		my ($k,$newcset) = split;
+		$newcsets{$k} = $newcset;
+	}
+	close(RSTATUS);
+}
+
+
+foreach my $old (@revs) {
+	printf("\nProcessing commit %s\n",$old);
+        $ENV{GIT_AUTHOR_EMAIL} = $csets{$old}{author}{email};
+        $ENV{GIT_AUTHOR_NAME} = $csets{$old}{author}{name};
+        $ENV{GIT_AUTHOR_DATE} = $csets{$old}{author}{datetime};
+        $ENV{GIT_COMMITTER_DATE} = $csets{$old}{committer}{datetime};
+        $ENV{GIT_COMMITTER_EMAIL} = $csets{$old}{committer}{email};
+        $ENV{GIT_COMMITTER_NAME} = $csets{$old}{committer}{name};
+
+	my @parents = ($old);
+	foreach my $p (@{$csets{$old}{parents}}) {
+		if (exists $newcsets{$p}) {
+			push @parents, $newcsets{$p};
+			printf("\t%s => %s\n",
+				$newcsets{$p},$p);
+		} else {
+			push @parents, $p;
+		}
+	}
+        my $commit = git_commit_tree($csets{$old}{tree},
+		$csets{$old}{comments},@parents);
+	$newcsets{$old} = $commit;
+        printf("\tNew commit: %s\n",$newcsets{$old});
+}
+
+open(RSTATUS,">",".git/info/ripple-status")
+	or die "Failed to save status in .git/info/ripple-status: " . $!;
+
+foreach my $k (keys %newcsets) {
+	printf RSTATUS "%s\t%s\n", $k, $newcsets{$k};
+}
+close(RSTATUS);
---
0.99.9.GIT