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git-svn: replace .rev_db with a more space-efficient .rev_map format

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Migrations are done automatically on an as-needed basis when new
revisions are to be fetched.  Stale remote branches do not get
migrated, yet.

However, unless you set noMetadata or useSvkProps it's safe to
just do:

  find $GIT_DIR/svn -name '.rev_db*' -print0 | xargs rm -f

to purge all the old .rev_db files.

The new format is a one-way migration and is NOT compatible with
old versions of git-svn.

This is the replacement for the rev_db format, which was too big
and inefficient for large repositories with a lot of sparse history
(mainly tags).

The format is this:

  - 24 bytes for every record,
    * 4 bytes for the integer representing an SVN revision number
    * 20 bytes representing the sha1 of a git commit

  - No empty padding records like the old format

  - new records are written append-only since SVN revision numbers
    increase monotonically

  - lookups on SVN revision number are done via a binary search

  - Piping the file to xxd(1) -c24 is a good way of dumping it for
    viewing or editing, should the need ever arise.

As with .rev_db, these files are disposable unless noMetadata or
useSvmProps is set.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Eric Wong
2007-12-08 23:27:41 -08:00
committed by Junio C Hamano
parent 591aa2536f
commit 060610c572
3 changed files with 218 additions and 110 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
t/lib-git-svn.sh
View File

@ -82,3 +82,29 @@ stop_httpd () {
test -z "$SVN_HTTPD_PORT" && return
"$SVN_HTTPD_PATH" -f "$GIT_DIR"/httpd.conf -k stop
}
convert_to_rev_db () {
perl -w -- - "$@" <<\EOF
use strict;
@ARGV == 2 or die "Usage: convert_to_rev_db <input> <output>";
open my $wr, '+>', $ARGV[1] or die "$!: couldn't open: $ARGV[1]";
open my $rd, '<', $ARGV[0] or die "$!: couldn't open: $ARGV[0]";
my $size = (stat($rd))[7];
($size % 24) == 0 or die "Inconsistent size: $size";
while (sysread($rd, my $buf, 24) == 24) {
my ($r, $c) = unpack('NH40', $buf);
my $offset = $r * 41;
seek $wr, 0, 2 or die $!;
my $pos = tell $wr;
if ($pos < $offset) {
for (1 .. (($offset - $pos) / 41)) {
print $wr (('0' x 40),"\n") or die $!;
}
}
seek $wr, $offset, 0 or die $!;
print $wr $c,"\n" or die $!;
}
close $wr or die $!;
close $rd or die $!;
EOF
}