git creates files ending in ~?

Just started using git on my mac. I have one file in my repository called README. When I change it, git puts another file in the directory called README~ containing the previous version.

1. Is it git doing this?
2. Why is git doing this?
3. How can I stop git doing this? (don't just want to add it to .gitignore, but I guess I could do that but I'd rather understand why I'm getting these files in the first place..)

(It's h开发者_JAVA百科ard to search for an answer on Google cos of trying to search on "~")

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The tilde suffix on file names is usually used by editors (Emacs, Vim in some modes/versions) on backup copies of files you edit. At one time on Mac, Vim seemed to create backups for me; it doesn't any more, but I'm not sure now whether that's because I tweaked a setting somewhere or whether vim changed its behaviour.

I have not seen git add tilde suffixes to file names (either on a Mac where I work mainly, or anywhere else).

To stop git wanting to add the files, add a line containing just *~ to .gitignore.

Vim has (at least) three settings related to this:

nobackup
  backupcopy=auto
  backupext=~

My ':set all' shows the values above. Yours probably shows 'backup' rather than 'nobackup'.