Add Link 4.1 Release Notes

Author: mkromberg

README.md

@@ -4,6 +4,9 @@ Link enables the use of text files as the primary storage mechanism for APL sour
 # Link Versions
 Although Link is developed as a GitHub project and it is possible to fork or clone it and configure Dyalog APL to use it in this fashion, most users of Link will be using a version which is delivered via the Dyalog installer and updated using the Dyalog patch mechanism. Currently supported versions are:
 
+## Version 4.1 (Dyalog v20.0 - compatible with v19.0)
+Version 4.1 will be shipped with Dyalog 20.0 and is being tested with Dyalog v19.0.
+
 ## Version 4.0 (Dyalog v19.0 - compatible with v18.2)
 Version 4.0 was shipped with Dyalog 19.0 and works with version 18.2.  The [online documentation](https://dyalog.github.io/link/) is maintained using markdown files which can be found in `docs` folder and deployed using `mkdocs` and `mike`, hosted with GitHub Pages.
 

docs/ReleaseNotes40.md

@@ -0,0 +1,41 @@
+# Version 4.1 Release Notes
+
+Link version 4.1 is distributed with Dyalog APL version 20.0 and is supported with version 19.0.
+You can select documentation for other versions of Link using the dropdown in the title bar.
+
+Apart from these release notes and minor corrections to the documentation, the documentation for version 4.1
+is identical to 4.0. Version 4.1 is primarily a bug fix release. A couple of significant groups of
+fixes are discussed below,
+and the [version 4.1 milestone on GitHub](https://github.com/Dyalog/link/milestone/5?closed=1) documents the full
+set of issues that are resolved by version 4.1.
+
+In addition to fixes, Link 4.1 recognises a new environment setting `ALWAYSREFORMAT`,
+which turns on automatic reformatting of all source code as it is written to source files.
+The following values are accepted:
+
+* ALWAYSREFORMAT=0: Do not reformat the source code
+* ALWAYSREFORMAT=1: Reformat using standard tab settings (4), as returned by (`61 ⎕ATX`)
+* ALWAYSREFORMAT=2: Use user-configured tab settings, as returned by `⎕CR` or `⎕NR`.
+
+## Significant fixes
+
+### Improved Error Messages
+
+Several error messages have been improved. For example, when a file
+cannot be imported to a classic interpreter due to a TRANSLATION ERROR,
+the file and the offending character is identified.
+
+### Improved File System Watcher
+
+The most significant improvement in version 4.1 is a complete rewrite of the code 
+that handles file system watcher events, which increased the performance and the
+robustness of Link, when faced with several more or less simultaneous file updates.
+
+For example, when using a source code management system like Git, a branch switch
+or a revert operation may cause a flurry of change to files. In Link 4.0, this
+could sometimes lead to functions disappearing, or failing to disappear when they should,
+as a result of processing messages in the wrong order.
+
+Although Link 4.1 is very much more robust than Link 4.0 in this regard, it is still not
+recommended to copy or unzip hundreds or thousands of files with an active file system
+watcher.

docs/ReleaseNotes41.md

@@ -4,13 +4,14 @@ repo_name: Dyalog/Link
 nav:
   - Overview:
     - index.md
+    - ReleaseNotes41.md
     - Discussion/TechDetails.md
     - Discussion/Workspaces.md
     - Discussion/History.md
 
   - Install and Upgrade:
     - Usage/Installation.md
-    - ReleaseNotes40.md
+    - ReleaseNotes41.md
 
   - Working with Link:
     - Usage/index.md