Makefile: automatically determine the bundle server version

Add a 'VERSION-FILE' target that generates a value for the Makefile
'VERSION' using 'git describe'.

The process for generating this file is based off of the 'GIT-VERSION-FILE'
target in the Git project's Makefile, with some minor changes for the sake
of efficiency.

If the 'VERSION' is set by the caller (e.g. with 'make VERSION=1.0.0'), the
'VERSION-FILE' target is a .PHONY (i.e., non-file, always run) target.

Conversely, if 'VERSION' is not set, 'VERSION-FILE' is instead a real file
target and is loaded into the Makefile with '-include VERSION-FILE'. Its
recipe runs the script 'generate-version.sh' to determine a version and
write 'VERSION := <string>' to 'VERSION-FILE' *if and only if* its contents
change. Finally, the 'VERSION-FILE' target depends on a .PHONY 'FORCE'
target, ensuring it is always re-run.

If the contents of 'VERSION-FILE' change as a result of
'generate-version.sh', the full 'Makefile' is re-evaluated. This ensures
that 'VERSION' is up-to-date with the contents of 'VERSION-FILE'.

Finally, compile the 'VERSION' into 'git-bundle-server' by setting the appropriate '-ldflags'.

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

.gitignore

@@ -1,5 +1,6 @@
 /git-bundle-server
 /git-bundle-web-server
+/VERSION-FILE
 /bin/
 /_dist/
 /_docs/

Makefile

@@ -1,10 +1,11 @@
 # Default target
 build:
 
-# Project metadata (note: to package, VERSION *must* be set by the caller)
+# Project metadata
+# By default, the project version is automatically determined using
+# 'git describe'. If you would like to set the version manually, set the
+# 'VERSION' variable to the desired version string.
 NAME := git-bundle-server
-VERSION :=
-PACKAGE_REVISION := 1
 
 # Installation information
 INSTALL_ROOT := /
@@ -22,6 +23,7 @@ GOARCH := $(shell go env GOARCH)
 # Packaging information
 SUPPORTED_PACKAGE_GOARCHES := amd64 arm64
 PACKAGE_ARCH := $(GOARCH)
+PACKAGE_REVISION := 1
 
 # Guard against environment variables
 APPLE_APP_IDENTITY =
@@ -30,12 +32,29 @@ APPLE_KEYCHAIN_PROFILE =
 E2E_FLAGS=
 INTEGRATION_FLAGS=
 
+# General targets
+.PHONY: FORCE
+
+ifdef VERSION
+# If the version is set by the user, don't bother with regenerating the version
+# file.
+.PHONY: VERSION-FILE
+else
+# If the version is not set by the user, we need to generate the version file
+# and load it.
+VERSION-FILE: FORCE
+	@scripts/generate-version.sh --version-file="$@"
+-include VERSION-FILE
+endif
+
 # Build targets
+LDFLAGS += -X '$(shell go list -m)/cmd/utils.Version=$(VERSION)'
+
 .PHONY: build
 build:
 	$(RM) -r $(BINDIR)
 	@mkdir -p $(BINDIR)
-	GOOS="$(GOOS)" GOARCH="$(GOARCH)" go build -o $(BINDIR) ./...
+	GOOS="$(GOOS)" GOARCH="$(GOARCH)" go build -o $(BINDIR) -ldflags "$(LDFLAGS)" ./...
 
 .PHONY: doc
 doc:
@@ -197,6 +216,7 @@ endif
 .PHONY: clean
 clean:
 	go clean ./...
+	$(RM) -r VERSION-FILE
 	$(RM) -r $(BINDIR)
 	$(RM) -r $(DISTDIR)
 	$(RM) -r $(DOCDIR)

scripts/generate-version.sh

@@ -0,0 +1,55 @@
+#!/bin/bash
+die () {
+	echo "$*" >&2
+	exit 1
+}
+
+write_version () {
+	if [ -n "$1" ]; then
+		echo "Setting VERSION to $1"
+	else
+		echo "No version found!"
+	fi
+	echo "VERSION := $1" >"$2"
+}
+
+# Parse script arguments
+for i in "$@"
+do
+case "$i" in
+	--version-file=*)
+	VERSION_FILE="${i#*=}"
+	shift # past argument=value
+	;;
+	*)
+	die "unknown option '$i'"
+	;;
+esac
+done
+
+if [ -z "$VERSION_FILE" ]; then
+    die "error: missing version file path"
+fi
+
+set -e
+
+# The pattern match used below is *less* restrictive than it should be (i.e.
+# "v<number>.<number>.<number>[-<optional string>]"), but we're limited by the
+# glob patterns used in 'git describe'.
+#
+# That said, we're explicitly specifying 'VERSION' for formal releases(based on
+# the more precise pattern match in 'release.yml', so it's not super important
+# to be strict here.
+VERSION_RAW="$(git describe --tags --match "v[0-9]*.[0-9]*.[0-9]*" 2>/dev/null || echo "")"
+VERSION="${VERSION_RAW:1}"
+
+if [ -r "$VERSION_FILE" ]
+then
+	CACHE_VERSION=$(sed -e 's/^VERSION := //' <"$VERSION_FILE")
+	if [ "$VERSION" != "$CACHE_VERSION" ]; then
+		write_version "$VERSION" "$VERSION_FILE"
+	fi
+else
+	# If the file doesn't exist, write unconditionally
+	write_version "$VERSION" "$VERSION_FILE"
+fi