Adding the ability to work with patches in memory.

[Douglas-Cleghorn]

This PR adds the ability to chain patch files for handling incremental diffs without having to write the entire file to disk at each step. It also enables working with large files (>2GB) in memory.

I didn't see a good way to accept an unknown number of patch files for the command line version. If you can give me some pointers, I'll try to get that implemented. Otherwise, this will only work for the library version.

[CLAassistant]

All committers have signed the CLA.

[borland]

Hi Douglas

Apologies on behalf of Octopus for taking so long to respond to this PR. We've recently re-assessed it and determined that it would be best not to merge.

While the ability to apply multiple patches without an interim file being written to disk is technically interesting, it does not satisfy any needs that we or our customers have at this time.

I also ran some performance tests and found that the BinaryDeltaStream is slower than the current implementation of DeltaApplier

Process: I checked out the code from your branch, bought it up to speed with our current Git Master, and used BenchmarkDotNet to run the same test through both our existing DeltaApplier and BinaryDeltaStream. The BinaryDeltaStream ends up using approximately the same amount of memory, but is measurably slower.

Small Delta

Method	Mean	Error	StdDev	Allocated
DeltaApplier.Apply	67.56 ms	1.766 ms	0.630 ms	178 MB
BinaryDeltaStream.Apply	73.20 ms	1.643 ms	0.427 ms	185.45 MB

Large Delta (I lost the memory allocation data for this, but it was approximately the same as the above test)

Method	Mean	Error	StdDev
DeltaApplier.Apply	2,669.43 ms	1,019.144 ms	363.436 ms
BinaryDeltaStream.Apply	7,848.26 ms	202.927 ms	52.700 ms

As such, we think it'd better to keep OctoDiff as simple as reasonably possible, and close this PR.

If you disagree, and/or you have a reason why this ability would be valuable to you, could you please reply and help us understand? we can re-open the PR if need be.

Kind regards

Orion Edwards Senior Software Engineer at Octopus Deploy