Why does Git use a colon (:<branch>) to delete remote branches?

Question

Why does Git use

git push <remote> :<branch>

as in

git push origin :featureA

to delete the branch featureA from the remote server?

I am interested in why the colon was used as the delete flag.

It's so different from git branch -d <localbranch>.

Why don't we do something like

git branch -d --remote origin <branchname>

or is there a deeper meaning behind the colon symbol that I didn't know?

Answer 1

The colon isn't a "delete flag". Note that git push and git pull both accept zero or more refspecs as their final argument(s). Now read about refspecs. A colon separates source from destination in a refspec. The command git push origin :foo has an empty source and essentially says "push nothing to branch foo of origin", or, in other words, "make branch foo on origin not exist".