[pointPen] Allow reverseFlipped parameter of DecomposingPointPen to take a ReverseFlipped enum value to control whether/how to reverse contour direction of flipped components, in addition to the existing True/False. This allows to set ReverseFlipped.ON_CURVE_FIRST to ensure that the decomposed outline starts with an on-curve point before being reversed, for better consistency with other segment-oriented contour transformations. The change is backward compatible, and the default behavior hasn't changed (#3934).

[filterPen] Added ContourFilterPointPen, base pen for buffered contour operations, and OnCurveStartPointPen filter to ensure contours start with an on-curve point (#3934).

[cu2qu] Fixed difference in cython vs pure-python complex division by real number (#3930).

[varLib.avar] Refactored and added some new sub-modules and scripts (#3926).

• varLib.avar.build module to build avar (and a missing fvar) binaries into a possibly empty TTFont,
• varLib.avar.unbuild module to print a .designspace snippet that would generate the same avar binary,
• varLib.avar.map module to take TTFont and do the mapping, in user/normalized space,
• varLib.avar.plan module moved from varLib.avarPlanner.

The bare fonttools varLib.avar script is deprecated, in favour of fonttools varLib.avar.build (or unbuild).

[interpolatable] Clarify linear_sum_assignment backend options and minimal dependency usage (#3927).

[post] Speed up build_psNameMapping (#3923).

[ufoLib] Added typing annotations to fontTools.ufoLib (#3875).