+filename suggests it is for the right package and version.
+.TP
+.BI --existing-package= package
+dgit push needs to canonicalise the suite name. But currently
+there is no way to ask the archive to do this without knowing the
+name of an existing package. Without --new we can just use the
+package we are trying to push. But with --new that will not work, so
+we guess that
+.B dpkg
+exists in the target suite. If it doesn't, you can use this option to
+specify a package which does. If the suite is empty, bad luck.
+.SH CONFIGURATION
+dgit looks at the following git config keys to control its behaviour.
+You may set them with git-config (either in system-global or per-tree
+configuration), or provide
+.BI -c key = value
+on the dgit command line.
+.TP
+.BI dgit-suite. suite .distro
+.TP
+.BI dgit.default.distro
+.TP
+.BI dgit.default.username
+.TP
+.BI dgit-distro. distro .git-url
+.TP
+.BI dgit-distro. distro .git-host
+.TP
+.BI dgit-distro. distro .git-proto
+.TP
+.BI dgit-distro. distro .git-path
+.TP
+.BI dgit-distro. distro .git-check
+.TP
+.BI dgit-distro. distro .git-create
+.TP
+.BI dgit-distro. distro .upload-host
+.TP
+.BI dgit-distro. distro .mirror
+.TP
+.BI dgit-distro. distro .archive-query
+.TP
+.BI dgit-distro. distro .archive-query-default-component
+.TP
+.BI dgit-distro. distro .ssh
+.TP
+.BR dgit.default. *
+for each
+.BR dgit-distro. \fIdistro\fR . *