* feat: add ability to forget length of typetracer created with `typetracer_from_report` by douglasdavis in https://github.com/scikit-hep/awkward/pull/2141
* feat: start hardening nplike signatures by agoose77 in https://github.com/scikit-hep/awkward/pull/2148
* feat: implement all ufuncs on TypeTracer. by jpivarski in https://github.com/scikit-hep/awkward/pull/2149
* feat: use `None` for unknown lengths (1 of 2) by agoose77 in https://github.com/scikit-hep/awkward/pull/2168
* feat: coerce backends to same zero-copy type (2 of 2) by agoose77 in https://github.com/scikit-hep/awkward/pull/2175
* feat: growable buffer move_to method by ianna in https://github.com/scikit-hep/awkward/pull/2178
* feat: add `ak.merge_union_of_records` by agoose77 in https://github.com/scikit-hep/awkward/pull/2185
* feat: add support for histogram module by agoose77 in https://github.com/scikit-hep/awkward/pull/2190
* feat: add `ak.approx_equal` by agoose77 in https://github.com/scikit-hep/awkward/pull/2198
Bug-fixes and performance
* fix: re-order cases to handle NumPy scalar types properly by agoose77 in https://github.com/scikit-hep/awkward/pull/2125
* fix: specify `dtype` for buffers in `from_rdataframe`. by agoose77 in https://github.com/scikit-hep/awkward/pull/2145
* fix: unify typestr with `_repr` by agoose77 in https://github.com/scikit-hep/awkward/pull/2158
* fix: update `type_to_name` for Layout builder `cxx_14` target by ianna in https://github.com/scikit-hep/awkward/pull/2165
* fix: Layout builders clean and length bug fixes by ianna in https://github.com/scikit-hep/awkward/pull/2171
* fix: support `mask_identity=True` for `axis=None` in `ptp`, `std`, etc. by agoose77 in https://github.com/scikit-hep/awkward/pull/2172
* fix: preserve dimensions for `keepdims=True`, `axis=None` reductions by agoose77 in https://github.com/scikit-hep/awkward/pull/2177
* fix: some usages of `len(layout)` under typetracer by agoose77 in https://github.com/scikit-hep/awkward/pull/2181
* fix: rdataframe memory check by ianna in https://github.com/scikit-hep/awkward/pull/2155
* fix: rework parameter merging rules by agoose77 in https://github.com/scikit-hep/awkward/pull/2179
* fix: don't raise `NotImplementedError` when reading empty array from Parquet by dsavoiu in https://github.com/scikit-hep/awkward/pull/2194
* fix: ignore object arrays by agoose77 in https://github.com/scikit-hep/awkward/pull/2206
* fix: ak.values_astype now turns 'unknown' type into the requested type. by jpivarski in https://github.com/scikit-hep/awkward/pull/2196
Other
* refactor: remove `to_arraylib` by agoose77 in https://github.com/scikit-hep/awkward/pull/2128
* refactor: move `Singleton` to its own module by agoose77 in https://github.com/scikit-hep/awkward/pull/2131
* refactor: move kernel logic to _kernels by agoose77 in https://github.com/scikit-hep/awkward/pull/2132
* refactor: use `nplike.asarray` by agoose77 in https://github.com/scikit-hep/awkward/pull/2134
* refactor: remove dead code by agoose77 in https://github.com/scikit-hep/awkward/pull/2139
* refactor: make `nplike.zeros` et al. use Array API type signatures by agoose77 in https://github.com/scikit-hep/awkward/pull/2137
* refactor: move typetracer ufunc handling to backend [1 of 2] by agoose77 in https://github.com/scikit-hep/awkward/pull/2150
* refactor: split `_nplikes.py` into `_nplikes/*.py` [2 of 2] by agoose77 in https://github.com/scikit-hep/awkward/pull/2152
* refactor: drop `UnknownScalar`, harden unknown scalar behavior by agoose77 in https://github.com/scikit-hep/awkward/pull/2154
* docs: fix bold docstring due to indent by agoose77 in https://github.com/scikit-hep/awkward/pull/2122
* docs: disable IPyParallel & load dependencies in reverse order by agoose77 in https://github.com/scikit-hep/awkward/pull/2126
* docs: improve error message by agoose77 in https://github.com/scikit-hep/awkward/pull/2201
* docs: add dsavoiu as a contributor for code by allcontributors in https://github.com/scikit-hep/awkward/pull/2204
* ci: test NumPy < 1.17 by agoose77 in https://github.com/scikit-hep/awkward/pull/2142
* ci: run header-only tests by agoose77 in https://github.com/scikit-hep/awkward/pull/2169
* chore: apply changes from flake8 by agoose77 in https://github.com/scikit-hep/awkward/pull/2130
* chore: isolate nox dependencies in `noxfile` by agoose77 in https://github.com/scikit-hep/awkward/pull/2136
* chore: drop unused nplike functions by agoose77 in https://github.com/scikit-hep/awkward/pull/2138
* chore: add helpful message if cpp install is not prepared by agoose77 in https://github.com/scikit-hep/awkward/pull/2146
* chore: move to Ruff by henryiii in https://github.com/scikit-hep/awkward/pull/2153
* chore(deps): bump pypa/cibuildwheel from 2.11.4 to 2.12.0 by dependabot in https://github.com/scikit-hep/awkward/pull/2133
* chore: update Ruff version by henryiii in https://github.com/scikit-hep/awkward/pull/2174
* chore: ruff rewrite `not in` by henryiii in https://github.com/scikit-hep/awkward/pull/2176
* chore: ruff rewrite dicts by henryiii in https://github.com/scikit-hep/awkward/pull/2183
New Contributors
* dsavoiu made their first contribution in https://github.com/scikit-hep/awkward/pull/2194
**Full Changelog**: https://github.com/scikit-hep/awkward/compare/v2.0.6...v2.0.7