The version is taken from git tags and generated with
git describe when qmake is run.
Then it is used in librecad/src/main/qc_applicationwindow.cpp at compile time.
The current default label, if there is no git on the build system, is
2.2.0-undef.
The latest tag in the code repository is
2.2.1-alpha, what you can see in the continuous build assets.
So, when your own build shows 2.2.0.1 you probably have git installed, but there are various reasons for a wrong version label.
To get the correct label, the first step is to git pull with --tags option to pull the tags from github.
Then all the makefiles need to be updated with qmake.
Finally a clean build to ensure that qc_applicationwindow.cpp is build new.
E.g. by
make clean
make
Probably it's enough to touch qc_applicationwindow.cpp to force make to build it, but a clean build from time to time doesn't hurt.
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