* putSaver: detect edit conflicts to prevent clobbering, if possible
if the server supplies an ETag, we send it back when saving, allowing
the server to detect edit conflicts and respond with 412 (cf.
https://www.w3.org/1999/04/Editing/)
caveats:
* this only kicks in after the first save, as we don't have access to
the ETag when first loading the document
* there's no recovery mechanism (e.g. resetting `this.etag` in order to
force clobbering), other than manually reloading the document
* putSaver: retrieve ETag upon initialization for clobbering protection
this addresses one of the caveats from the previous commit
(2d75cb83af) - while theoretically prone
to a race condition, it seems unlikely that saving will be triggered
before the server responds
* putSaver: simplify URI extraction
this simplifies the approach introduced in
f51f6bf774, with the purpose of removing
the fragment identifier
* putSaver: localize error message
* putSaver: switch to built-in HTTP helper
in the process, fixed ETag assignment in `#save` method (was
`this.etag`, now `self.etag`) as well as a syntax error due to a missing
closing brace
* putSaver: consolidate URI handling
When renaming an existing tiddler, the edit template now shows a
checkbox that determines whether or not to relink references to the
tiddler in the list or tags fields of other tiddlers.
* return all wikiparserrules w/o operand
* simpler layout & code / updated instruction details
Also wanted to link each rule to the official docs using a dictionary at
`$:/language/Docs/ParserRules/`. However, without #2194 this is not
doable.
There have been long standing problems with the buttons not working in
Firefox, and now a [further
problem](https://groups.google.com/d/msg/tiddlywiki/GlsruQyPOag/BAhnI2mt
BgAJ) has come to light, and been similarly hard to resolve.
On balance, I’ve decided to remove the undo/redo buttons from the
toolbar (the ctrl/cmd-Z shortcut is still operational), thus avoiding
the problems, and saving some space in the core.
The present implementation of relative dates doesn’t auto-update, nor
does it work effectively in static renderings. Until that’s fixed, I
think it is better to switch to absolute dates.
“-do-not-delete” flag for savetiddlers command was introduced in 5.1.10
without consistency with the already implemented “noclean” flag for the
rendertiddlers command
