git如何解释冒号和路径？

Question

I was toying with a syntax to refer a commit by its commit message and then I got this error:

$ git show :/A
fatal: ambiguous argument ':/A': both revision and filename
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

The error message is pretty clear about how to solve it, but I haven't found any documentation explaining how does git interpret a colon followed by a path. Only if followed by a branch name.
Can you please give me some references to learn more about this?

Answer 1

It's actually a bit trickier than you might expect, as :/A could be three things.

There are multiple different bits of Git documentation that talk about this, but there are two main places to look:

• The gitrevisions documentation describes how : -prefixes work when something is a revision specifier .
• The gitglossary defines how : -prefixes work when something is a pathspec .

When it's just a file name, :/A just means the file named :/A .

As a pathspec , :/A uses the "magic signature" character / , no terminating : , and the name A , so it refers to the file named A in the root directory (of the repository or work-tree), rather than the file :/A in the current directory.

As a revision specifier , :/A searches commit messages, and A becomes a regular expression (although in this case it's a trivial regex that just matches the letter A ):

... This name returns the youngest matching commit which is reachable from any ref, including HEAD.

Using the -- you'll force Git to treat it as a pathspec , where you may want to add :(literal) in front to protect it from interpretation.