git: mention rev-parse --show-cdup and GIT_DIR as workarounds

Author: lazka

web/docs/git.md

@@ -20,4 +20,6 @@ They depend on Tcl/Tk and we only provide mingw builds for those. In all environ
 
 ### Some tool I use fails to work with the git in MSYS2, but works fine with the official one
 
-One common issue with external tools integrating git, is that they get confused by Unix paths, for example when figuring out the project root path via `git rev-parse --show-toplevel`. This can be worked around by using `git rev-parse --show-prefix` instead which outputs a relative path from the root to the current working directory, which is both a valid Unix and Windows path.
+One common issue with external tools integrating git, is that they get confused by Unix paths, for example when figuring out the project root path via `git rev-parse --show-toplevel`. This can be worked around by using `git rev-parse --show-prefix` instead which outputs a relative path from the root to the current working directory, which is both a valid Unix and Windows path. Or `git rev-parse --show-cdup` which outputs a relative path from the current working directory to the root, which is also a valid Unix and Windows path.
+
+If all fails you can `export GIT_DIR=/dev/null` to make git not find any repository at all, which usually makes tools skip any git related logic.