I have seen colleagues using git add -A :/ for staging files in repositories, but I am unable to find what that does in the documentation. What am I missing?
(This answer originally talked about refspecs, which turned out to be irrelevant and incorrect.)
As lrineau's answer correctly points out, the : character in this case is part of the syntax of a pathspec.
Documentation on pathspecs is annoyingly difficult to find, but there's a "gitglossary" man page, available either by typing man gitglossary or visiting this web page.
The relevant part:
A pathspec that begins with a colon
:has special meaning. In the short form, the leading colon:is followed by zero or more "magic signature" letters (which optionally is terminated by another colon :), and the remainder is the pattern to match against the path. The optional colon that terminates the "magic signature" can be omitted if the pattern begins with a character that cannot be a "magic signature" and is not a colon.In the long form ... [snip].
The "magic signature" consists of an ASCII symbol that is not alphanumeric.
top /
The magic wordtop(mnemonic:/) makes the pattern match from the root of the working tree, even when you are running the command from inside a subdirectory.
The conclusion is the same as in my original answer: :/ refers to the root directory of the current working tree.