tag-from-cargo-toml.sh

#!/bin/bash

dry=0
if [[ $# -gt 0 && $1 == "-n" ]]; then
	dry=1
	shift
fi
prefix="v"
if [[ $# -gt 0 ]]; then
	if [[ $1 = -* || $# -gt 1 ]]; then
		echo "Usage: $0 [-n] [prefix]"
		exit 1
	fi
	prefix="$1"
	shift
fi

function tag() {
	local v=$1
	local hash=$2
	local tag="${prefix}${v}"
	if git rev-parse "$tag" > /dev/null 2>&1; then
		existing=$(git rev-parse "$tag^{}")
		if [[ $hash == $existing ]]; then
			echo "$hash $tag (already tagged)"
		else
			echo "$hash $tag (already tagged at $existing)"
		fi
		return
	fi
	if [[ $dry -eq 0 ]]; then
		git tag -a -m "Release $tag" "$tag" "$hash"
	fi
	echo "$hash $tag"
}

# in case we're in a subdir:
cargo_toml=$(git ls-files --full-name Cargo.toml)

was=""
last_hash=""
last_name=""
function walk() {
	local cargo_toml=$1
	local start_hash=$2
	for hash in $(git log --first-parent --format=oneline "$start_hash" -- "$cargo_toml" | awk '{print $1}'); do
		n=$(git show "$hash:$cargo_toml" | grep -P '^name\s*=' | head -n1 | sed -e 's/[^"]*"//' -e 's/".*//')
		v=$(git show "$hash:$cargo_toml" | grep -P '^version\s*=' | head -n1 | sed -e 's/[^"]*"//' -e 's/".*//')
		if [[ -z "$last_name" ]]; then
			last_name=$n
		elif [[ -z "$n" ]]; then
			# probably a workspace -- try a little harder to retrace versions
			local cargo_toml="${cargo_toml%Cargo.toml}$last_name/Cargo.toml"
			if ! git cat-file -e $hash:$cargo_toml 2>/dev/null; then
				echo "!! crate disappeared -- stopping." > /dev/stderr
				return
			fi

			n=$(git show "$hash:$cargo_toml" | grep -P '^name\s*=' | head -n1 | sed -e 's/[^"]*"//' -e 's/".*//')
			if [[ -z "$n" ]]; then
				echo "!! could not determine name of crate in workspace -- stopping." > /dev/stderr
				return
			elif [[ $last_name != $n ]]; then
				echo "!! name changed from $n (in workspace) to $last_name -- stopping." > /dev/stderr
				return
			else
				# restart within workspace
				echo ".. following crate into workspace $last_name"
				walk "$cargo_toml" "$hash"
				return
			fi
		elif [[ $last_name != $n ]]; then
			echo "!! name changed from $n to $last_name -- stopping." > /dev/stderr
			break
		fi
		if [[ $was == $v ]]; then
			# same version -- keep walking until we hit the previous
			last_hash=$hash
			continue
		fi
		if [[ $was = ${v}-* ]]; then
			# pushed an alpha/beta/rc *after* main version?
			# no, main version cannot have been released as non-alpha first
			continue
		fi
		if [[ -z "$was" ]]; then
			# start search
			was="$v"
			last_hash="$hash"
			continue
		fi

		# this hash has a different hash than the previous one. so tag the last
		# hash with the last version number, since that was the first hash at
		# which that version number appeared.
		tag "$was" "$last_hash"
		last_hash="$hash"
		was=$v
	done
}
walk "$cargo_toml" "HEAD"

# tag the first commit that has this Cargo.toml
tag "$was" "$last_hash"