Hello,

In Mbed TLS long-time support branches (currently 2.7.x and 2.16.x), we make bug fixes, but we preserve backward compatibility as much as possible. This means that as much as possible, we don't change existing behavior unless it's definitely wrong, we don't add new APIs, we don't increase the code size. We also preserve backward compatibility with build and deployment processes for projects that use the library. We don't create new source files, we don't change the name of makefile targets, we don't add new tools requirements or tool version requirements to build the library and its tests, etc. For example:

* We added Python as a requirement to build the tests shortly before the 2.16 release, but kept the existing Perl script in the 2.7 LTS. * We've changed config.pl to a Python script in development, but kept it in Perl in LTS branches. * We've dropped support for older Visual Studio version in development, but kept it in LTS branches.

How far should this extend to non-core files, such as documentation and higher-level test scripts? For example:

* We're considering tweaking the format of the ChangeLog file. Should we preserve the format strictly in LTS branches? * How about renaming ChangeLog to CHANGES or CHANGES.md? * We're considering rewriting some multi-configuration test scripts and maintainer sanity checks such as tests/scripts/depends-*.pl, tests/scripts/all.sh, tests/scripts/check-names.sh, etc., in Python. (Note that we've already done that with new scripts added to all.sh: Python was not a requirement to pass all.sh in 2.7.0, but it is now.)