convert/svn: do not try converting empty head revisions (issue3347)
Subversion conversion works by picking trunk and branches heads, computing a
revision graph from them and converting the selected commits. By design we fail
to convert empty revisions so we have to be careful when discovering the
revision graph. In this particular issue, the source svn repository was a
partial mirror made by svnsync. The funny part is svnsync preserves all
revisions including empty ones. Also, we trusted ra.stat(path,
stop).created_rev to give us the latest revision with changes in path history
up to stop. This assumption broke at least when path is '', that is the
repository root, which always returned 'stop' revision despited being empty.
The workaround is to first trust ra.stat() but if the returned revision appear
empty, search the whole path history from stop to r1 until some changes are
found.
SVN-fs-dump-format-version: 2
UUID: b70c45d5-2b76-4722-a373-d9babae61626
Revision-number: 0
Prop-content-length: 260
Content-length: 260
K 8
svn:date
V 27
2012-04-18T11:35:14.752409Z
K 17
svn:sync-from-url
V 73
file:///Users/pmezard/dev/hg/hg-pmezard/tests/svn/temp/svn-repo/trunk/dir
K 18
svn:sync-from-uuid
V 36
56625b9e-e7e9-45be-ab61-052d41f0e1dd
K 24
svn:sync-last-merged-rev
V 1
4
PROPS-END
Revision-number: 1
Prop-content-length: 112
Content-length: 112
K 10
svn:author
V 7
pmezard
K 8
svn:date
V 27
2012-04-18T11:35:14.769622Z
K 7
svn:log
V 10
init projA
PROPS-END
Node-path: trunk
Node-kind: dir
Node-action: add
Prop-content-length: 10
Content-length: 10
PROPS-END
Revision-number: 2
Prop-content-length: 107
Content-length: 107
K 10
svn:author
V 7
pmezard
K 8
svn:date
V 27
2012-04-18T11:35:15.052989Z
K 7
svn:log
V 6
adddir
PROPS-END
Node-path: trunk/dir
Node-kind: dir
Node-action: add
Prop-content-length: 10
Content-length: 10
PROPS-END
Node-path: trunk/dir/a
Node-kind: file
Node-action: add
Prop-content-length: 10
Text-content-length: 2
Text-content-md5: 60b725f10c9c85c70d97880dfe8191b3
Text-content-sha1: 3f786850e387550fdab836ed7e6dc881de23001b
Content-length: 12
PROPS-END
a
Revision-number: 3
Prop-content-length: 105
Content-length: 105
K 10
svn:author
V 7
pmezard
K 8
svn:date
V 27
2012-04-18T11:35:16.050353Z
K 7
svn:log
V 4
addb
PROPS-END
Revision-number: 4
Prop-content-length: 105
Content-length: 105
K 10
svn:author
V 7
pmezard
K 8
svn:date
V 27
2012-04-18T11:35:17.050768Z
K 7
svn:log
V 4
addc
PROPS-END