prepare changelog for v0.3.1

And start adding links for the major changes, so any interested users
can read more into each topic.

We also make the release links use the "v" prefix for consistency.

CHANGELOG.md

@@ -1,6 +1,14 @@
 # Changelog
 
-## [0.3.0] - 2022-02-22
+## [v0.3.1] - 2022-03-21
+
+This bugfix release resolves a number of issues:
+
+* Avoid "too many open files" error regression introduced by [v0.3.0] - [#208]
+* Use the `go.mod` relative to each Go file when deriving flag defaults - [#211]
+* Remove unintentional debug prints when directly formatting files
+
+## [v0.3.0] - 2022-02-22
 
 This is gofumpt's third major release, based on Go 1.18's gofmt.
 The jump from Go 1.17's gofmt should bring a noticeable speed-up,
@@ -20,7 +28,7 @@ The following changes are included as well:
   grouped with standard library imports
 * `format.Options` gains a `ModulePath` field per the last bullet point
 
-## [0.2.1] - 2021-12-12
+## [v0.2.1] - 2021-12-12
 
 This bugfix release resolves a number of issues:
 
@@ -29,13 +37,13 @@ This bugfix release resolves a number of issues:
 * Don't group interface members of different kinds
 * Account for leading comments in composite literals
 
-## [0.2.0] - 2021-11-10
+## [v0.2.0] - 2021-11-10
 
 This is gofumpt's second major release, based on Go 1.17's gofmt.
 The jump from Go 1.15's gofmt should bring a mild speed-up,
 as walking directories with `filepath.WalkDir` uses fewer syscalls.
 
-gofumports is now removed, after being deprecated in [0.1.0].
+gofumports is now removed, after being deprecated in [v0.1.0].
 Its main purpose was IDE integration; it is now recommended to use gopls,
 which in turn implements goimports and supports gofumpt natively.
 IDEs which don't integrate with gopls (such as GoLand) implement goimports too,
@@ -60,15 +68,15 @@ Finally, the following changes are made to the gofumpt tool:
 * The `format` Go API now also applies the `gofmt -s` simplification
 * Add support for `//gofumpt:diagnose` comments
 
-## [0.1.1] - 2021-03-11
+## [v0.1.1] - 2021-03-11
 
 This bugfix release backports fixes for a few issues:
 
 * Keep leading empty lines in func bodies if they help readability
 * Avoid breaking comment alignment on empty field lists
 * Add support for `//go-sumtype:` directives
 
-## [0.1.0] - 2021-01-05
+## [v0.1.0] - 2021-01-05
 
 This is gofumpt's first release, based on Go 1.15.x. It solidifies the features
 which have worked well for over a year.
@@ -89,8 +97,12 @@ those building programs with gofumpt.
 Finally, this release adds the `-version` flag, to print the tool's own version.
 The flag will work for "master" builds too.
 
-[0.3.0]: https://github.com/mvdan/gofumpt/releases/tag/v0.3.0
-[0.2.1]: https://github.com/mvdan/gofumpt/releases/tag/v0.2.1
-[0.2.0]: https://github.com/mvdan/gofumpt/releases/tag/v0.2.0
-[0.1.1]: https://github.com/mvdan/gofumpt/releases/tag/v0.1.1
-[0.1.0]: https://github.com/mvdan/gofumpt/releases/tag/v0.1.0
+[v0.3.1]: https://github.com/mvdan/gofumpt/releases/tag/v0.3.1
+[#208]: https://github.com/mvdan/gofumpt/issues/208
+[#211]: https://github.com/mvdan/gofumpt/pull/211
+
+[v0.3.0]: https://github.com/mvdan/gofumpt/releases/tag/v0.3.0
+[v0.2.1]: https://github.com/mvdan/gofumpt/releases/tag/v0.2.1
+[v0.2.0]: https://github.com/mvdan/gofumpt/releases/tag/v0.2.0
+[v0.1.1]: https://github.com/mvdan/gofumpt/releases/tag/v0.1.1
+[v0.1.0]: https://github.com/mvdan/gofumpt/releases/tag/v0.1.0