Prep for JuMP 0.21.6 (#2426)

* Prep for JuMP 0.21.6

* Update NEWS.md

* Update NEWS.md

NEWS.md

@@ -1,6 +1,54 @@
 JuMP release notes
 ==================
 
+Version 0.21.6 (January 29, 2020)
+---------------------------------
+
+For a detailed list of the closed issues and pull requests from this release,
+see the [tag notes](https://github.com/jump-dev/JuMP.jl/releases/tag/v0.21.6).
+A summary of changes are as follows:
+
+- New features:
+  * Added support for skew symmetric variables via
+    `@variable(model, X[1:2, 1:2] in SkewSymmetricMatrixSpace())`.
+  * `lp_sensitivity_report` has been added which significantly improves the
+    performance of querying the sensitivity summary of an LP.
+    `lp_objective_perturbation_range` and `lp_rhs_perturbation_range` are
+    deprecated.
+  * Dual warm-starts are now supported with `set_dual_start_value` and
+    `dual_start_value`.
+  * `∈` (`\in<tab>`) can now be used in macros instead of `=` or `in`.
+  * Use `haskey(model::Model, key::Symbol)` to check if a name `key` is
+    registered in a model.
+  * Added `unregister(model::Model, key::Symbol)` to unregister a name `key` 
+    from `model`.
+  * Added `callback_node_status` for use in callbacks.
+  * Added `print_bridge_graph` to visualize the bridging graph generated by
+    MathOptInterface.
+  * Improved error message for containers with duplicate indices.
+- Bug fixes:
+  * Various fixes to pass tests on Julia 1.6.
+  * Fixed a bug in the printing of nonlinear expressions in IJulia.
+  * Fixed a bug when nonlinear expressions are passed to user-defined functions.
+  * Some internal functions that were previously exported are now no longer
+    exported.
+  * Fixed a bug when relaxing a fixed binary variable.
+  * Fixed a `StackOverflowError` that occured when `SparseAxisArray`s had a
+    large number of elements.
+  * Removed an unnecessary type assertion in `list_of_constraint_types`.
+  * Fixed a bug when copying models with registered expressions.
+- Documentation and general maintenance:
+  * The documentation has been significantly overhauled. It now has distinct
+    sections for the manual, API reference, and examples. The existing examples
+    in `/examples` have now been moved to `/docs/src/examples` and rewritten
+    using `Literate.jl`, and they are now included in the documentation.
+  * JuliaFormatter has been applied to most of the codebase. This will continue
+    to roll out over time, as we fix upstream issues in the formatter, and will
+    eventually become compulsory.
+  * The root cause of a large number of method invalidations has been resolved.
+  * We switched continuous integration from Travis and Appveyor to Github
+    Actions.
+
 Version 0.21.5 (September 18, 2020)
 -----------------------------------
 

Project.toml

@@ -1,7 +1,7 @@
 name = "JuMP"
 uuid = "4076af6c-e467-56ae-b986-b466b2749572"
 repo = "https://github.com/jump-dev/JuMP.jl.git"
-version = "0.21.5"
+version = "0.21.6"
 
 [deps]
 Calculus = "49dc2e85-a5d0-5ad3-a950-438e2897f1b9"

README.md

@@ -4,14 +4,14 @@
 [![Powered by NumFOCUS](https://img.shields.io/badge/powered%20by-NumFOCUS-orange.svg?style=flat&colorA=E1523D&colorB=007D8A)](https://numfocus.org)
 
 JuMP is a domain-specific modeling language for [mathematical optimization](https://en.wikipedia.org/wiki/Mathematical_optimization)
-embedded in [Julia](https://julialang.org/). You can find out more about us by 
+embedded in [Julia](https://julialang.org/). You can find out more about us by
 visiting [jump.dev](https://jump.dev).
 
-**Latest Release**: 0.21.5 (`release-0.21` branch):
+**Latest Release**: 0.21.6 (`release-0.21` branch):
   * Installation via the Julia package manager:
     * `import Pkg; Pkg.add("JuMP")`
   * Get help:
-    * Read the [Documentation](https://jump.dev/JuMP.jl/v0.21.5/)
+    * Read the [Documentation](https://jump.dev/JuMP.jl/v0.21.6/)
     * Ask a question on the [Community forum]
     * Explore the [JuMPTutorials](https://github.com/jump-dev/JuMPTutorials.jl)
   * Testing status:
@@ -30,8 +30,8 @@ visiting [jump.dev](https://jump.dev).
 
 ## Need help?
 
-Use the [Community forum] to search for answers to previously asked questions, 
-or ask a new question. 
+Use the [Community forum] to search for answers to previously asked questions,
+or ask a new question.
 
 The post [PSA: make it easier to help you](https://discourse.julialang.org/t/psa-make-it-easier-to-help-you/14757),
 describes the best practices for asking a question.
@@ -40,15 +40,15 @@ describes the best practices for asking a question.
 
 ## Bug reports
 
-Please report any issues via the Github [issue tracker]. All types of issues 
-are welcome and encouraged; this includes bug reports, documentation typos, 
+Please report any issues via the Github [issue tracker]. All types of issues
+are welcome and encouraged; this includes bug reports, documentation typos,
 feature requests, etc.
 
 [issue tracker]: https://github.com/jump-dev/JuMP.jl/issues
 
 ## Citing JuMP
 
-If you find JuMP useful in your work, we kindly request that you cite the 
+If you find JuMP useful in your work, we kindly request that you cite the
 following paper ([pdf](https://mlubin.github.io/pdf/jump-sirev.pdf)):
 
 ```bibtex
@@ -64,7 +64,7 @@ following paper ([pdf](https://mlubin.github.io/pdf/jump-sirev.pdf)):
 }
 ```
 
-For an earlier work where we presented a prototype implementation of JuMP, see 
+For an earlier work where we presented a prototype implementation of JuMP, see
 [here](https://dx.doi.org/10.1287/ijoc.2014.0623):
 
 ```bibtex