Date: Tue, 6 Feb 2024 17:16:41 -0800 Create a script for automating kernel version changes. This generates a pair of commits which cause history to remain attached to all versioned configuration files.
Crucially this makes `git blame` work without needing --find-copies-harder, which is too slow for routine use. This also updates *everything*, which greatly simplifies rebasing patches which effect multiple devices. Credit to Christian Marangi who knew of the technique: <https://lists.openwrt.org/pipermail/openwrt-devel/2023-October/041672.html> Signed-off-by: Elliott Mitchell <ehem+open...@m5p.com> --- v3: Dust off knowledge of PerlOO. Confine the fast-importer interface to an object. Better layer the lowest I/O layer. If fast-import grows a \0 command separation mode, we should be mostly ready (issue will be the commit message). Switch to SPDX. Try to match what the other scripts have. I was kind of hoping for more review activity, the near-silence is almost deafening. Using a script to handle this job seems best. I feel what this script produces is rather easier for most developers to handle. v2: Major tweaking. No longer try to do `git merge --ff-only <hash>`, but instead advise user to do so. Add usage message. Add statement about strategy. Adjust commit messages. Add advice to run `git bisect skip` if someone ends up on that commit. --- scripts/kernel_upgrade.pl | 280 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 280 insertions(+) create mode 100755 scripts/kernel_upgrade.pl diff --git a/scripts/kernel_upgrade.pl b/scripts/kernel_upgrade.pl new file mode 100755 index 0000000000..c2e5fb6078 --- /dev/null +++ b/scripts/kernel_upgrade.pl @@ -0,0 +1,280 @@ +#!/usr/bin/env perl +######################################################################### +# SPDX-License-Identifier: GPL-3.0-or-later # +# # +# Copyright (C) 2024 Elliott Mitchell <ehem+open...@m5p.com> # +######################################################################### + +use warnings; +use strict; + +# +# I'm not certain the technique originated here, but this comes from: +# <https://devblogs.microsoft.com/oldnewthing/20190919-00/?p=102904> +# +# Problem is copying a file in git causes the new file to be created +# without any history. Files can move around without losing their +# history, but that only leaves the history on the new location. +# +# As such this can be solved with two commits. The first commit moves +# files from their old name to their new name. The second merges the +# original commit with the rename commit. The merge commit then has +# files in both locations with the full history. +# +# +# Note, git handles discarded data by garbage collection. When doing +# development on this script, beware this script is an excellent +# garbage generator. Frequent use of `git gc` and `git prune` may be +# needed. +# + + +sub gethead() +{ + open(my $fd, '-|', 'git', 'rev-parse', 'HEAD'); + $_=<$fd>; + chop; + return $_; +} + +sub getlist($$) +{ + my ($target, $from)=@_; + my $ret=[]; + + local $/="\0"; + open(my $fd, '-| :raw :bytes', 'git', 'ls-tree', '-trz', '--full-name', +'--name-only', 'HEAD', '--', $target)||die("failed to read git tree"); + + while(<$fd>) { + chop($_); + push(@$ret, substr($_, 0, -length($from))) +if(substr($_, -length($from)) eq $from); + } + + @$ret=sort({length($b)-length($a)} @$ret); + + return $ret; +} + +{ # start of interface to git fast-import +package GitImporter; + +# git fast-import's protocol uses *linefeeds* +local $/="\n"; + +sub new() +{ + my $class=shift; + my $self={}; + my @child; + (pipe($child[0], $self->{out})&&pipe($self->{in}, $child[1])) || +die("pipe() failed"); + binmode($self->{out}); + binmode($self->{in}); + + $self->{pid}=fork(); + if($self->{pid}==0) { + close($self->{out}); + close($self->{in}); + + open(STDIN, '<&', $child[0]); + close($child[0]); + + open(STDOUT, '>&', $child[1]); + close($child[1]); + + exec('git', 'fast-import', '--done'); + die('exec() of git failed'); + } elsif(!$self->{pid}) { + die('fork() failed'); + } + close($child[0]); + close($child[1]); + $self->{out}->autoflush(1); + + return bless($self, $class); +} + +sub send($) +{ + my $self=shift; + my ($data)=@_; + return print({$self->{out}} $data); +} + +sub putcmd($) +{ + my $self=shift; + my ($data)=@_; + return $self->send("$data\n"); +} + +sub recv() +{ + my $self=shift; + return $_=readline($self->{in}); +} + +sub getres() +{ + my $self=shift; + $_=$self->recv(); + chomp; + return $_; +} + +sub ls($$) +{ + my $self=shift; + my ($commit, $name)=@_; + + $commit.=' ' if($commit); + $self->putcmd("ls $commit$name"); + $self->getres(); + + die('git ls failed') unless(/^([0-8]+)\s+[a-z]+\s+([0-9a-z]+)\s+.+$/); + + return [$1, $2]; +} + +sub commit($$$) +{ + my $self=shift; + my ($dest, $message, $mark)=@_; + + use feature 'state'; + use Digest::SHA qw(sha1_hex); + + state $author=undef; + unless($author) { + $author=['', '']; + open(my $user, '-|', 'git', 'config', '--get', 'user.name'); + while(<$user>) { + chomp; + $author->[0].=$_; + } + $author->[0]=[split(/,/, [getpwuid($<)]->[6])]->[0] +unless($author->[0]); + + open(my $email, '-|', 'git', 'config', '--get', 'user.email'); + while(<$email>) { + chomp; + $author->[1].=$_; + } + $author->[1]='anonym...@example.com' unless($author->[1]); + + $author=$author->[0].' <'.$author->[1].'>'; + } + + $_=sha1_hex(time()); + $self->putcmd("commit $_"); + $self->putcmd("mark $mark"); + $self->putcmd("committer $author ".time()." +0000"); + + $_=length($message); + $self->putcmd("data $_"); + $self->send($message); + $self->putcmd("from $dest"); +} + +sub DESTROY() +{ + my $self=shift; + + $self->putcmd('done'); + close($self->{out}); + delete $self->{out}; + + 0 while(waitpid($self->{pid}, 0)!=$self->{pid}); + delete $self->{pid}; + close($self->{in}); + delete $self->{in}; + + print(STDERR <<~"__GIT_STATUS__") if($?); + WARNING: git returned error exit status: $? + + This likely means `git gc` needs to be run, but the return codes of + `git fast-import` are undocumented. + + __GIT_STATUS__ +} +} # end of interface to git fast-import + + +die(<<"__USAGE__") if(@ARGV!=2); +Usage: $0 <old-version> <new-version> + +Copies all kernel configuration files and patches from the old version +to the new version. Git history is preserved on the copies by using a +move/merge strategy. Must be run while somewhere inside the git +repository directory, but it does not matter where. +__USAGE__ + +my ($from, $to)=@ARGV; + + +my $target='target/linux'; + +my $start=gethead(); + +my $list=getlist($target, $from); + +die("no files matching \"$from\" found") unless(@$list); + + +my $git=GitImporter->new(); + +$git->commit($start, <<"__TMP__", ':1'); +kernel: add configs and patches for $to + +This is a special tool-generated commit. + +Copy configuration and patches from $from to $to. + +If you see this commit during a `git bisect` session, the recommended +course of action is to run `git bisect skip`. +__TMP__ + +foreach my $name (@$list) { + my $new=$git->ls($start, "$name$from"); + $git->putcmd("M $new->[0] $new->[1] $name$to"); + $git->putcmd("D $name$from"); +} +$git->putcmd(''); + + +$git->commit(':1', <<"__TMP__", ':2'); +kernel: finish update from $from to $to + +This is a special tool-generated commit. + +Merge the add commit into HEAD to create all files with full history. +__TMP__ + +$git->putcmd("merge $start"); + +foreach my $name (@$list) { + my $new=$git->ls($start, "$name$from"); + $git->putcmd("M $new->[0] $new->[1] $name$from"); +} +$git->putcmd(''); + + +$git->putcmd('get-mark :2'); +my $result=$git->getres(); + +undef($git); + +print(<<"__END__"); +Result is commit $result. + +Depending on the setup of your development environment, you now likely +want to run one of two commands: + + `git merge --ff-only $result` +or: + `git branch linux-$to $result` +__END__ + +exit(0); -- 2.39.2 _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org https://lists.openwrt.org/mailman/listinfo/openwrt-devel
