docs/auth.md: update

1 files changed, 23 insertions, 2 deletions

diff --git a/docs/auth.md b/docs/auth.md
index 3b64fd9..4eabcd5 100644
--- a/docs/auth.md
+++ b/docs/auth.md
@@ -25,5 +25,26 @@ When using HTTPS, there're multiple options to access the private repositories.
 3. Use per-application passwords.  This option is pretty cool.  Both GitHub (in
    the form of "personal access tokens") and Bitbucket (calls them "app
    passwords") support creating one-purpose passwords that are supposed to be
-   used by a single app only.  They allow to bypass the 2FA also.  cgitize will
-   support this option.
+   used by a single app only.  They allow to bypass the 2FA also.  Let's do
+   this!
+
+Passing the access tokens to Git is tricky though.  First, simply including
+them in the clone URL would be incredibly stupid, since that URL is going to be
+visible on the cgit web pages.  There's an option to use the Git
+`credentials.helper`, but I thought that it was quite hard to get right in a
+cross-platform way.
+
+Now, there's `url.<url>.insteadOf`.  It can be used to make Git rewrite every
+URL to include the access token.
+
+* I don't want to set it permanently to avoid leaking the access token.
+* I don't want to set it in the repository's `--local` .git/config, since it is
+  probably readable by other users.
+* I don't want to ever use it on the command line to avoid leaking it.
+
+Eventually, the option I settled on is to
+
+1. `chmod 0600 ~/.gitconfig`.
+2. Append the section to ~/.gitconfig from Python (_not_ by using `git
+   config`).
+3. Undo everything once we're done.