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[PATCH] archimport - add merge detection
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We now keep track of the patches merged in each branch since they have
diverged, using the records that the Arch "logs" provide. Merge parents
for a commit are defined if we are merging a series of patches that starts
from the mergebase.

If patches from a related branch are merged out-of-order, we keep track of
how much has been merged sequentially -- the tip of that sequential merge
is our new parent from that branch.

This mechanism works very well for branches that merge in dovetail and/or
flying fish patterns, probably less well for others.

Signed-off-by: Martin Langhoff <martin@catalyst.net.nz>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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martin@catalyst.net.nz authored and Junio C Hamano committed Sep 10, 2005
1 parent 866ff2f commit b779d5f
Showing 1 changed file with 180 additions and 4 deletions.
184 changes: 180 additions & 4 deletions git-archimport.perl
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Original file line number Diff line number Diff line change
Expand Up @@ -61,7 +61,7 @@ END
exit(1);
}

getopts("hviC:t:") or usage();
getopts("ThviC:t:") or usage();
usage if $opt_h;

@ARGV >= 1 or usage();
Expand All @@ -76,6 +76,10 @@ END


my @psets = (); # the collection
my %psets = (); # the collection, by name

my %rptags = (); # my reverse private tags
# to map a SHA1 to a commitid

foreach my $root (@arch_roots) {
my ($arepo, $abranch) = split(m!/!, $root);
Expand All @@ -96,6 +100,7 @@ END
if (%ps) {
my %temp = %ps; # break references
push (@psets, \%temp);
$psets{$temp{id}} = \%temp;
%ps = ();
}

Expand Down Expand Up @@ -158,7 +163,8 @@ END

if (%ps) {
my %temp = %ps; # break references
push (@psets, \%temp);
push (@psets, \%temp);
$psets{ $temp{id} } = \%temp;
%ps = ();
}
close ABROWSE;
Expand All @@ -183,6 +189,24 @@ END
} else {
die "Need to start from an import or a tag -- cannot use $psets[0]{id}";
}
} else { # progressing an import
# load the rptags
opendir(DIR, ".git/archimport/tags")
|| die "can't opendir: $!";
while (my $file = readdir(DIR)) {
# skip non-interesting-files
next unless -f ".git/archimport/tags/$file";
next if $file =~ m/--base-0$/; # don't care for base-0
my $sha = ptag($file);
chomp $sha;
# reconvert the 3rd '--' sequence from the end
# into a slash
# $file = reverse $file;
# $file =~ s!^(.+?--.+?--.+?--.+?)--(.+)$!$1/$2!;
# $file = reverse $file;
$rptags{$sha} = $file;
}
closedir DIR;
}

# process patchsets
Expand Down Expand Up @@ -345,6 +369,9 @@ END
}
}

if ($ps->{merges}) {
push @par, find_parents($ps);
}
my $par = join (' ', @par);

#
Expand Down Expand Up @@ -391,7 +418,8 @@ END
print " * Committed $ps->{id}\n";
print " + tree $tree\n";
print " + commit $commitid\n";
# print " + commit date is $ps->{date} \n";
$opt_v && print " + commit date is $ps->{date} \n";
$opt_v && print " + parents: $par \n";
}

sub branchname {
Expand Down Expand Up @@ -556,7 +584,7 @@ sub tag {
or die "Cannot write tag $tag: $!\n";
close(C)
or die "Cannot write tag $tag: $!\n";
print "Created tag '$tag' on '$commit'\n" if $opt_v;
print " * Created tag ' $tag' on '$commit'\n" if $opt_v;
} else { # read
open(C,"<.git/refs/tags/$tag")
or die "Cannot read tag $tag: $!\n";
Expand Down Expand Up @@ -587,6 +615,8 @@ sub ptag {
or die "Cannot write tag $tag: $!\n";
close(C)
or die "Cannot write tag $tag: $!\n";
$rptags{$commit} = $tag
unless $tag =~ m/--base-0$/;
} else { # read
# if the tag isn't there, return 0
unless ( -s ".git/archimport/tags/$tag") {
Expand All @@ -599,6 +629,152 @@ sub ptag {
die "Error reading tag $tag: $!\n" unless length $commit == 40;
close(C)
or die "Cannot read tag $tag: $!\n";
unless (defined $rptags{$commit}) {
$rptags{$commit} = $tag;
}
return $commit;
}
}

sub find_parents {
#
# Identify what branches are merging into me
# and whether we are fully merged
# git-merge-base <headsha> <headsha> should tell
# me what the base of the merge should be
#
my $ps = shift;

my %branches; # holds an arrayref per branch
# the arrayref contains a list of
# merged patches between the base
# of the merge and the current head

my @parents; # parents found for this commit

# simple loop to split the merges
# per branch
foreach my $merge (@{$ps->{merges}}) {
my $branch = branchname($merge);
unless (defined $branches{$branch} ){
$branches{$branch} = [];
}
push @{$branches{$branch}}, $merge;
}

#
# foreach branch find a merge base and walk it to the
# head where we are, collecting the merged patchsets that
# Arch has recorded. Keep that in @have
# Compare that with the commits on the other branch
# between merge-base and the tip of the branch (@need)
# and see if we have a series of consecutive patches
# starting from the merge base. The tip of the series
# of consecutive patches merged is our new parent for
# that branch.
#
foreach my $branch (keys %branches) {
my $mergebase = `git-merge-base $branch $ps->{branch}`;
die "Cannot find merge base for $branch and $ps->{branch}" if $?;
chomp $mergebase;

# now walk up to the mergepoint collecting what patches we have
my $branchtip = git_rev_parse($ps->{branch});
my @ancestors = `git-rev-list --merge-order $branchtip ^$mergebase`;
my %have; # collected merges this branch has
foreach my $merge (@{$ps->{merges}}) {
$have{$merge} = 1;
}
my %ancestorshave;
foreach my $par (@ancestors) {
$par = commitid2pset($par);
if (defined $par->{merges}) {
foreach my $merge (@{$par->{merges}}) {
$ancestorshave{$merge}=1;
}
}
}
# print "++++ Merges in $ps->{id} are....\n";
# my @have = sort keys %have; print Dumper(\@have);

# merge what we have with what ancestors have
%have = (%have, %ancestorshave);

# see what the remote branch has - these are the merges we
# will want to have in a consecutive series from the mergebase
my $otherbranchtip = git_rev_parse($branch);
my @needraw = `git-rev-list --merge-order $otherbranchtip ^$mergebase`;
my @need;
foreach my $needps (@needraw) { # get the psets
$needps = commitid2pset($needps);
# git-rev-list will also
# list commits merged in via earlier
# merges. we are only interested in commits
# from the branch we're looking at
if ($branch eq $needps->{branch}) {
push @need, $needps->{id};
}
}

# print "++++ Merges from $branch we want are....\n";
# print Dumper(\@need);

my $newparent;
while (my $needed_commit = pop @need) {
if ($have{$needed_commit}) {
$newparent = $needed_commit;
} else {
last; # break out of the while
}
}
if ($newparent) {
push @parents, $newparent;
}


} # end foreach branch

# prune redundant parents
my %parents;
foreach my $p (@parents) {
$parents{$p} = 1;
}
foreach my $p (@parents) {
next unless exists $psets{$p}{merges};
next unless ref $psets{$p}{merges};
my @merges = @{$psets{$p}{merges}};
foreach my $merge (@merges) {
if ($parents{$merge}) {
delete $parents{$merge};
}
}
}
@parents = keys %parents;
@parents = map { " -p " . ptag($_) } @parents;
return @parents;
}

sub git_rev_parse {
my $name = shift;
my $val = `git-rev-parse $name`;
die "Error: git-rev-parse $name" if $?;
chomp $val;
return $val;
}

# resolve a SHA1 to a known patchset
sub commitid2pset {
my $commitid = shift;
chomp $commitid;
my $name = $rptags{$commitid}
|| die "Cannot find reverse tag mapping for $commitid";
# the keys in %rptag are slightly munged; unmunge
# reconvert the 3rd '--' sequence from the end
# into a slash
$name = reverse $name;
$name =~ s!^(.+?--.+?--.+?--.+?)--(.+)$!$1/$2!;
$name = reverse $name;
my $ps = $psets{$name}
|| (print Dumper(sort keys %psets)) && die "Cannot find patchset for $name";
return $ps;
}

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