I think your search for a “standard” naming convention will be in vain. Here are my proposals, based on existing, well-known programs:
A) C:\users\OddThinking\Documents\My Source\Widget\foo.src
---
Vim calls it file root (:help filename-modifiers)
B) C:\users\OddThinking\Documents\My Source\Widget\foo.src
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C) C:\users\OddThinking\Documents\My Source\Widget\foo.src
___ (without dot)
D) C:\users\OddThinking\Documents\My Source\Widget\foo.src
____ (with dot)
also file extension. Simply store without the dot, if there is no dot on a file, it has no extension
E) C:\users\OddThinking\Documents\My Source\Widget\foo.src
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top of the tree
No convention, git calls it base directory
F) C:\users\OddThinking\Documents\My Source\Widget\foo.src
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path from top of the tree to the leaf
relative path
G) C:\users\OddThinking\Documents\My Source\Widget\foo.src
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one node of the tree
no convention, maybe a simple directory
H) C:\users\OddThinking\Documents\My Source\Widget\foo.src
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I) C:\users\OddThinking\Documents\My Source\Widget\foo.src
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