Avoid Doxygen XML rebuild if no source files change #1045
Description
Hello,
I'm somewhat new to Breathe and Sphinx.
I joined a project where we use Breathe to run Doxygen and generate the required XML files.
I noticed that a full rebuild is triggered every time, even if no source files are changed. The whole process (Breathe and Sphinx workflow) takes ~10 minutes due to the size of our codebase, and makes quick iteration pretty much impossible.
It would be nice to have Breathe keep a cache with file time stamps for the source->XML generation step (similarly to how it's done for the XML->rst step), to avoid re-generating identical XML files every time.
I hacked together a very rough implementation, where XML files are only rebuilt if some of the source files they depend on have changed since the previous build. This seems to solve my problem. It's pretty simple but I can definitely share it with you if it helps.
Please let me know what you think.
Thank you!