chore(util) new 'changelog' script and Makefile target

E.g:

    $ make changelog
    misc(*) fix log format specifier of 'ssize_t' arguments
    feat(proxy-wasm) implement initial metrics facilities
    refactor(shm/kv) allow retrieving items by key hash
    fix(proxy-wasm) resume content phase after request_body read EAGAIN
    refactor(lua-bridge) remove entry thread sleep timer handling
    fix(proxy-wasm) cancel dispatches when immediately producing a response
    feat(proxy-wasm) dispatch errors do not interrupt filter chains
    refactor(lua-bridge) rewrite for full yielding support
    fix(lib) prevent a segfault loading an empty .wat module with V8
    feat(wasmtime) new 'cache_config' directive for compilation cache
    feat(proxy-wasm) consistent context checks for all header setters
    feat(proxy-wasm) allow setting ':status' response pseudo-header
    refactor(wasm) fix conflicting values in our '*_CONF' definitions
    feat(http) implement 'postpone_rewrite' + 'postpone_access' directives
    refactor(wasmx) store ngx_wa_conf_t as our core module context
    fix(ffi) allow 'load()' to fail and be invoked again
    fix(shm/kv) ensure memory realloc when value is replaced by a larger one
    feat(*) implement ipc modules & generalize WasmX namespace

Changelog author can paste the list in CHANGELOG.md and
filter-out/format the last bits.

Makefile

@@ -80,7 +80,7 @@ update:
 
 .PHONY: todo
 todo:
-	@/bin/grep -rIFn -- 'TODO' src/ t/
+	@/bin/grep -rIFn -- 'TODO' src/ lib/ t/ util/
 
 .PHONY: act-build
 act-build:
@@ -93,6 +93,10 @@ act-build:
 act: act-build
 	@act --reuse --pull=false
 
+.PHONY: changelog
+changelog:
+	@util/changelog.sh
+
 .PHONY: coverage
 coverage: clean
 	NGX_BUILD_GCOV=1 make

docs/DEVELOPER.md

@@ -174,8 +174,9 @@ release artifacts).
 | `lint`             | Lint the sources and test cases
 | `reindex`          | Automatically format the `.t` test files
 | `update`           | Run `cargo update` in all workspaces
-| `todo`             | Search the project for "TODOs" (source + tests)
+| `todo`             | Search the project for "TODOs" (source, tests, scripts)
 | `act`              | Build and run the CI environment
+| `changelog`        | Print all changelog-worthy commits since the last release
 | `clean`            | Clean the latest build
 | `cleanup`          | Does `clean` and also cleans some more of the build environment to free-up disk space
 | `cleanall`         | Destroy the build environment

util/changelog.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+set -e
+
+SCRIPT_NAME=$(basename $0)
+NGX_WASM_DIR=${NGX_WASM_DIR:-"$(
+    cd $(dirname $(dirname ${0}))
+    pwd -P
+)"}
+if [[ ! -f "${NGX_WASM_DIR}/util/_lib.sh" ]]; then
+    echo "Unable to source util/_lib.sh" >&2
+    exit 1
+fi
+
+source $NGX_WASM_DIR/util/_lib.sh
+
+###############################################################################
+
+cd $NGX_WASM_DIR
+
+# TODO: be smarter about grabbing the proper tag once we have more than just
+# prerelease tags
+LATEST_TAG=$(git describe --tags --abbrev=0)
+
+# Only show user-facing commits. Include refactor(), misc() and use best
+# judgement whether or not to include them in the final release description).
+git --no-pager log --format=oneline $LATEST_TAG.. \ | sed "s/^[^ ]* //" \ |
+    $(which grep) -v -E '^(chore|tests|style|hotfix|docs)'