Fix tag updates

Closes #3

See merge request !9

svn lacks a rename/replace function, requiring first that an existing
tag be deleted before an update is copied into place. svn is, fortunately,
generally smart enough to sort out the history and show only the updated
files in the resulting commit.

Support tag updates

See merge request !8

Add support for WP.org's static assets

See merge request !7

Support updates to existing tags

See merge request !6

Base image now provides rsync

See merge request !5

Explain gitattributes

See merge request !4

Fix readme typo

See merge request !3

Include release ref in info output

See merge request !2

Add CI badge

See merge request !1