Single root fast path - Githubissues

When a repository has only one root and is the first one to write to it the push step can be skipped and the packfile sent as is. This makes the process quite faster at the expense of disk space.

Rename references to add the repository ID
Change configuration (adds repository remote)
Delete remote "origin" used to clone the repository
Create siva file and copy temporary repository to it
Use copier to send the new siva file to the remote location

This process skips RootedTransactioner to download and upload siva files. To be able to use Copier it is added to Archiver.

Also moved logging of time spent to copy siva files from pushChangesToRootedRepository to tidy it a bit.

a: current version b: fast path

repo	time a	time b	size a	size b
cangallo	881.5ms	347.6ms (-60%)	0.1MiB	0.1MiB(0%)
octoprint-tft	9s	1s (-84%)	2.8MiB	3MiB(+7%)
upsilon	2m20s	14.6s (-89%)	96.2MiB	98MiB (+2%)
numpy	7m55s	7m26s (-6%)	95MiB	95MiB (0%)
tensorflow	38m32s	37m10s (-3%)	706MiB	706MiB (0%)
bismuth	17m1s	3m48s (-77%)	491MiB	497MiB (+2%)

Note: the repositories "numpy" and "tensorflow" have more than one root so it uses the same code as before. Left here for completion.

Fixes #377

Raw output of regression:

#### Comparing latest - local:HEAD ####
## Repo cangallo ##
Memory: 24236032 -> 19181568 (-20.855163089403415), true
Wtime: 881.486544ms -> 347.626016ms (-60.56366165017716), true
Stime: 250ms -> 30ms (-88), true
Utime: 1.07s -> 170ms (-84.11214953271028), true
FileSize: 0.11093711853027344 -> 0.11100196838378906 (0.05845640699413717), true
## Repo octoprint-tft ##
Memory: 62439424 -> 32030720 (-48.7011283127788), true
Wtime: 9.02956085s -> 1.014957052s (-88.75961889110033), true
Stime: 780ms -> 60ms (-92.3076923076923), true
Utime: 9.78s -> 960ms (-90.1840490797546), true
FileSize: 2.824666976928711 -> 3.0296154022216797 (7.255666843806531), true
## Repo upsilon ##
Memory: 709877760 -> 238895104 (-66.34700825111072), true
Wtime: 2m20.496095764s -> 14.631545255s (-89.58579939503977), true
Stime: 13.31s -> 1.93s (-85.49962434259955), true
Utime: 2m34.51s -> 13.57s (-91.21739693223739), true
FileSize: 96.22913646697998 -> 98.00282859802246 (1.8431965578856715), true
## Repo numpy ##
Memory: 1207513088 -> 1165721600 (-3.460955282001879), true
Wtime: 7m55.740268897s -> 7m26.875567723s (-6.067323508460316), true
Stime: 1m11.01s -> 1m1.45s (-13.462892550345021), true
Utime: 10m3.09s -> 9m30.9s (-5.33751181415709), true
FileSize: 95.48885822296143 -> 95.49099731445312 (0.0022401477319003577), true
## Repo tensorflow ##
Memory: 5028749312 -> 4931715072 (-1.9295899234517262), true
Wtime: 38m32.777768384s -> 37m10.59889938s (-3.55325401892896), true
Stime: 4m42.72s -> 4m6.65s (-12.758205998868139), true
Utime: 50m46.15s -> 49m29.17s (-2.5271244029348523), true
FileSize: 706.3063344955444 -> 706.3145418167114 (0.0011620058841542164), true
## Repo bismuth ##
Memory: 2306678784 -> 1018535936 (-55.84404976258715), true
Wtime: 17m1.713103943s -> 3m48.809022005s (-77.60535505300076), true
Stime: 44s -> 9.4s (-78.63636363636364), true
Utime: 17m40.02s -> 3m50.74s (-78.23248617950604), true
FileSize: 491.3974657058716 -> 497.367374420166 (1.214883903749669), true

src-d / borges

Single root fast path #378