added support for removing tiles that shouldn't exist with --check-tiles

--check-tiles is now activated by shrinking maps
better detection for --forcerender situtations
Also cleaned up some docs and comments
Moved tiledir creation to TileSet constructor

docs/running.rst

@@ -116,34 +116,57 @@ only have to use once-in-a-while.
 .. cmdoption:: --forcerender
 
     Forces The Overviewer to re-render every tile regardless of whether it
-    thinks it needs updating or not. This is similar to deleting your output
-    directory and rendering from scratch.
+    thinks it needs updating or not. It does no tile mtime checks, nor does it
+    check any last modification time of the world. It unconditionally renders
+    every tile that exists.
 
-    This is the default mode for first-time renders. This option overrides
+    The caveat with this option is that it does *no* checks, period. Meaning it
+    will not detect tiles that do exist, but shouldn't (this can happen if your
+    world shrinks for some reason. For that specific case,
+    :option:`--check-tiles` is actually more appropriate).
+
+    This is the default mode for first-time renders. This option conflicts with
     :option:`--check-tiles` and :option:`--no-tile-checks`
 
 .. cmdoption:: --check-tiles
 
-    Forces The Overviewer to check each tile on disk and compare its
-    modification time to the modification time of the part of the world that
-    tile renders. This is slightly slower than the default, but can be useful if
-    there are some tiles that somehow got skipped.
+    Forces The Overviewer to check each tile on disk and check to make sure it
+    is up to date. This also checks for tiles that shouldn't exist and deletes
+    them.
+    
+    This is slightly slower than :option:`--no-tile-checks` due to the disk-io
+    involved in reading tile mtimes and reading the world's region file headers
+    for chunk mtimes, but can be useful if there are some tiles that somehow got
+    skipped.
+
+    The caveat with this option is that it compares the tile mtimes on disk with
+    the chunk mtimes reported by Minecraft. Thus, if the Minecraft world was not
+    updated since the last render, tiles will not be detected as needing
+    updates. This means you cannot use this option in response to a changed
+    configuration setting.
 
     This option is the default when The Overviewer detects the last render was
-    interrupted midway through. This option overrides :option:`--forcerender`
-    and :option:`--no-tile-checks`
+    interrupted midway through. This option conflicts with
+    :option:`--forcerender` and :option:`--no-tile-checks`
 
 .. cmdoption:: --no-tile-checks
 
-    With this option, The Overviewer will not do any checking of tiles on disk
-    to determine what tiles need updating. Instead, it will look at the time
-    that the last render was performed, and render parts of the map that were
-    changed since then. This is the fastest option, but could cause problems if
-    the clocks of the Minecraft server and the machine running The Overviewer
-    are not in sync.
+    With this option, The Overviewer will determine which tiles to render by
+    looking at the saved last-render timestamp and comparing it to the
+    last-modified time of the chunks of the world. It builds a tree of tiles
+    that need updating and renders only those tiles.
 
-    This option is the default unless the condition for :option:`--forcerender`
-    or :option:`--check-tiles` is in effect.  This option overrides
+    This option does not do *any* checking of tile mtimes on disk, and thus is
+    the cheapest option: only rendering what needs updating while minimising
+    disk IO.
+
+    The caveat is that the *only* thing to trigger a tile update is if Minecraft
+    updates a chunk. Any other reason for needing to re-render a tile requires a
+    different mode to detect the needed update. It could also cause problems if
+    the system clock of the machine running Minecraft is not stable.
+    
+    **This option is the default** unless :option:`--forcerender` or
+    :option:`--check-tiles` is in effect.  This option conflicts with
     :option:`--forcerender` and :option:`--check-tiles`.
 
 .. cmdoption:: -p <procs>, --processes <procs>
@@ -154,6 +177,23 @@ only have to use once-in-a-while.
 
     This option can also be specified in the config file as :ref:`processes <processes>`
 
+.. cmdoption:: -v, --verbose
+
+    Activate a more verbose logging format and turn on debugging output. This
+    can be quite noisy but also gives a lot more info on what The Overviewer is
+    doing.
+
+.. cmdoption:: -q, --quiet
+
+    Turns off one level of logging for quieter output. You can specify this more
+    than once. One ``-q`` will suppress all INFO lines. Two will suppress all
+    INFO and WARNING lines. And so on for ERROR and CRITICAL log messages.
+
+    If :option:`--verbose<-v>` is given, then the first ``-q`` will counteract
+    the DEBUG lines, but not the more verbose logging format. Thus, you can
+    specify ``-v -q`` to get only INFO logs and higher (no DEBUG) but with the
+    more verbose logging format.
+
 .. _installing-textures:
 
 Installing the Textures