obshistory: omit duplicate notes of obsolescence operations
When folding changesets, it's possible to provide a --note flag to e.g. fold or
prune, which will store a note for that operation. But since there would be
more than one marker for the fold operation and the provided note would be
stored in all of them, _markersnotes() previously would return the same text
message many times. We don't really want to see the same thing over and over,
so let's make notes a set().
This will also make unrelated operations with the same note show the message
only once, which is probably an improvement too.
Doc is generated with sphinx.
You can generate the doc with:
```
make
```
# Tutorials
For updating the tutorials, you need to have the docgraph extension installed
(https://pypi.python.org/pypi/hg-docgraph).
Then run the test-topic-tutorial.t and test-tutorial.t to update the output if
needed.
You'll need the dot binary (likely installed by the graphviz package in your
package manager) in order to have graphviz graphs rendered in the html output.
Simply run make in the docs directory should takes care of the conversion of
the tutorial .t files into .rst files. Then sphinx should do the rest of the
jobs by rendering graphviz graphs.