What is git's “filemode”?

For something that exists in EVERY single git repo... on earth... there sure isn't very much info out there regarding filemode. The first 100 responses from google were all over the place, and a question with this' title handn't been asked.. so here goes.. What is filemode? For me, it's in every repo's ./git/config file, near the top, a lá...

 [core]
    filemode = true

What is it? What does it mean? Does it bear any relation to

    bare = false

which I also don't really get... I use git like a madman, and know what a million other of git's endless, and IMHO, arbitrarily concocted / half-brained config parameters do.. but not this one... I'm sure it's a simple thing (maybe related to permissions? or war triggers a change flag?), so if you know more about how to manipulate the setting / and to what effect.. that would be good to know...

VonC

A git bare repo (detailed here) has no relation with filemode.
It is used for pushing to it, because since it has no working tree, there is no concern about maintaining said working tree in sync with what you just pushed.

what is a "fake" file? and what constitutes a "working" directory?

There is no "fake" file. It is just that a bare repo only contains git's administrative and control files, not actual data file you could work with and modify.
Those are checked out in a "working directory", when the repo is not bare.

The git config man page

core.fileMode

If false, the executable bit differences between the index and the working tree are ignored; useful on broken filesystems like FAT (File Allocation Table).
See git-update-index.

The command honors core.filemode configuration variable.
If your repository is on a filesystem whose executable bits are unreliable, this should be set to false.
This causes the command to ignore differences in file modes recorded in the index and the file mode on the filesystem if they differ only on executable bit.
On such an unfortunate filesystem, you may need to use git update-index --chmod=.

For me, it's in every repo's ./git/config file, near the top,