Upload same filename replaces file

[johrstrom]

When you upload a file that shares the same name of a file that already exists - we currently replace it. Instead, we should do what Web browsers and curl, wget and likely others all do, append numbers to the filenname like so:

foo.txt
foo_1.txt

# this tends to be strange/bad in Linux, so I'm tempted to just use underscore `_N`. 
foo (1).txt 

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[lukew3]

Related to #281/#2094

[johrstrom]

Does #2094 also fix this? or is it just related?

[lukew3]

Does #2094 also fix this? or is it just related?

Just related. The code to generate a new filename is written in #2094 but would have to be applied to this context