paper: make actual changeset entries have backgrounds on /graph
This patch removes a separate container for backgrounds only and puts
backgrounds on changeset elements themselves. This makes it so that JS code
doesn't need to create background elements separately anymore.
There's a bit of manipulating positions of elements: every changeset entry has
a "fg" element that gets a higher z-index than <canvas> element. This
prioritizes text information, so that even if it somehow gets close to the
graph drawn on <canvas> (which has z-index of 5), it'll still be on top of it.
This can happen if commit message has a long first line and browser window is
narrow, for example.
#require unix-permissions no-root
$ hg init a
$ cd a
$ echo foo > b
$ hg add b
$ hg ci -m "b"
$ chmod -w .hg/store
$ cd ..
$ hg clone a b
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets 97310831fa1a
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ chmod +w a/.hg/store # let test clean up
$ cd b
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
$ cd ..