Explicitly selecting a source format by putting the format in
debian/source/format is recommended. This allows for
future removal of the 1.0 default for the package source format and,
depending on the source format, may allow unambiguous declaration of
whether this package is native or non-native.
If you don't have a reason to stay with the old format for this package, please consider switching to "3.0 (quilt)" (for packages with a separate upstream tarball) or to "3.0 (native)" (for Debian native packages).
If you wish to keep using the old format, please create that file and put "1.0" in it to be explicit about the source package version. If you have problems with the 3.0 format, the dpkg maintainers are interested in hearing, at firstname.lastname@example.org, the (technical) reasons why the new formats do not suit you.
For more information please consult:
The tag is present in Lintian version
That is the most recent version we know about.
We use semantic versions.
The patch number is a commit step indicator relative to the
release tag in our Git
You can find the detection logic for this version at commit ce6249d. For merge requests, please use the latest version in the Lintian check debian/source-dir.