Consider using htmldiff for XEP diffs

[Flowdalic]

IIRC we use(d) DaisyDiff for XEP version diffs. Probably https://github.com/cygri/htmldiff would be an good alternative.

Example output:

• http://geekplace.eu/xeps/xep-nonza/diff-side-by-side.html │
• http://geekplace.eu/xeps/xep-nonza/diff.html

[horazont]

The runtime of htmldiff for e.g. XEP-0060 on my i7 machine is worrying (it hasn’t returned for minutes now, I set up a /usr/bin/time -v measurement; will post the results once available) (measurements below). We for sure can’t rebuild the whole history of XEPs on each push, that will probably take days, especially on Docker Hub or Travis.

We need something incremental here, bearing in mind that the build for a diff between large XEPs can take quite a bit of CPU time. Does anyone have a suggestion how that could be done with current infrastructure? @intosi @Kev maybe?

	Command being timed: "htmldiff /home/horazont/Builds/xep-attic/content/xep-0060-1.10.html /home/horazont/Builds/xep-attic/content/xep-0060-1.11.html"
	User time (seconds): 388.88
	System time (seconds): 0.37
	Percent of CPU this job got: 99%
	Elapsed (wall clock) time (h:mm:ss or m:ss): 6:29.46
	Average shared text size (kbytes): 0
	Average unshared data size (kbytes): 0
	Average stack size (kbytes): 0
	Average total size (kbytes): 0
	Maximum resident set size (kbytes): 37604
	Average resident set size (kbytes): 0
	Major (requiring I/O) page faults: 0
	Minor (reclaiming a frame) page faults: 165177
	Voluntary context switches: 13
	Involuntary context switches: 4092
	Swaps: 0
	File system inputs: 0
	File system outputs: 0
	Socket messages sent: 0
	Socket messages received: 0
	Signals delivered: 0
	Page size (bytes): 4096
	Exit status: 0

[Neustradamus]

Detail : It was "XEP Diff Tool" on http://xmpp.org/extensions/diff/

[Neustradamus]

Example:

• http://www.aptest.com/standards/htmldiff/htmldiff.pl?oldfile=https://xmpp.org/extensions/attic/xep-XXXX-X.X.X.html&newfile=https://xmpp.org/extensions/attic/xep-XXXX-X.X.X.html

Linked to:

• The return of XEP Diff Tool xmpp.org#412