# Copyright 1999-2018 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2

# @ECLASS: git-r3.eclass
# @MAINTAINER:
# Michał Górny <mgorny@gentoo.org>
# @BLURB: Eclass for fetching and unpacking git repositories.
# @DESCRIPTION:
# Third generation eclass for easing maintenance of live ebuilds using
# git as remote repository.

case "${EAPI:-0}" in
	0|1|2|3)
		die "Unsupported EAPI=${EAPI} (obsolete) for ${ECLASS}"
		;;
	4|5|6|7)
		;;
	*)
		die "Unsupported EAPI=${EAPI} (unknown) for ${ECLASS}"
		;;
esac

EXPORT_FUNCTIONS src_unpack

if [[ ! ${_GIT_R3} ]]; then

PROPERTIES+=" live"

if [[ ! ${_INHERITED_BY_GIT_2} ]]; then
	# NB: We omit git for older EAPI's to avoid circular deps in board sysroots.
	if [[ ${EAPI:-0} != [0123456] ]]; then
		BDEPEND=">=dev-vcs/git-1.8.2.1[curl]"
	fi
fi

# @ECLASS-VARIABLE: EGIT_CLONE_TYPE
# @DESCRIPTION:
# Type of clone that should be used against the remote repository.
# This can be either of: 'mirror', 'single', 'shallow'.
#
# This is intended to be set by user in make.conf. Ebuilds are supposed
# to set EGIT_MIN_CLONE_TYPE if necessary instead.
#
# The 'mirror' type clones all remote branches and tags with complete
# history and all notes. EGIT_COMMIT can specify any commit hash.
# Upstream-removed branches and tags are purged from the local clone
# while fetching. This mode is suitable for cloning the local copy
# for development or hosting a local git mirror. However, clones
# of repositories with large diverged branches may quickly grow large.
#
# The 'single+tags' type clones the requested branch and all tags
# in the repository. All notes are fetched as well. EGIT_COMMIT
# can safely specify hashes throughout the current branch and all tags.
# No purging of old references is done (if you often switch branches,
# you may need to remove stale branches yourself). This mode is intended
# mostly for use with broken git servers such as Google Code that fail
# to fetch tags along with the branch in 'single' mode.
#
# The 'single' type clones only the requested branch or tag. Tags
# referencing commits throughout the branch history are fetched as well,
# and all notes. EGIT_COMMIT can safely specify only hashes
# in the current branch. No purging of old references is done (if you
# often switch branches, you may need to remove stale branches
# yourself). This mode is suitable for general use.
#
# The 'shallow' type clones only the newest commit on requested branch
# or tag. EGIT_COMMIT can only specify tags, and since the history is
# unavailable calls like 'git describe' will not reference prior tags.
# No purging of old references is done. This mode is intended mostly for
# embedded systems with limited disk space.
: ${EGIT_CLONE_TYPE:=single}

# @ECLASS-VARIABLE: EGIT_MIN_CLONE_TYPE
# @DESCRIPTION:
# 'Minimum' clone type supported by the ebuild. Takes same values
# as EGIT_CLONE_TYPE. When user sets a type that's 'lower' (that is,
# later on the list) than EGIT_MIN_CLONE_TYPE, the eclass uses
# EGIT_MIN_CLONE_TYPE instead.
#
# This variable is intended to be used by ebuilds only. Users are
# supposed to set EGIT_CLONE_TYPE instead.
#
# A common case is to use 'single' whenever the build system requires
# access to full branch history, or 'single+tags' when Google Code
# or a similar remote is used that does not support shallow clones
# and fetching tags along with commits. Please use sparingly, and to fix
# fatal errors rather than 'non-pretty versions'.
: ${EGIT_MIN_CLONE_TYPE:=shallow}

# @ECLASS-VARIABLE: EGIT3_STORE_DIR
# @DESCRIPTION:
# Storage directory for git sources.
#
# This is intended to be set by user in make.conf. Ebuilds must not set
# it.
#
# EGIT3_STORE_DIR=${DISTDIR}/git3-src

# @ECLASS-VARIABLE: EGIT_MIRROR_URI
# @DEFAULT_UNSET
# @DESCRIPTION:
# 'Top' URI to a local git mirror. If specified, the eclass will try
# to fetch from the local mirror instead of using the remote repository.
#
# The mirror needs to follow EGIT3_STORE_DIR structure. The directory
# created by eclass can be used for that purpose.
#
# Example:
# @CODE
# EGIT_MIRROR_URI="git://mirror.lan/"
# @CODE

# @ECLASS-VARIABLE: EGIT_REPO_URI
# @REQUIRED
# @DESCRIPTION:
# URIs to the repository, e.g. https://foo. If multiple URIs are
# provided, the eclass will consider the remaining URIs as fallbacks
# to try if the first URI does not work. For supported URI syntaxes,
# read the manpage for git-clone(1).
#
# URIs should be using https:// whenever possible. http:// and git://
# URIs are completely unsecured and their use (even if only as
# a fallback) renders the ebuild completely vulnerable to MITM attacks.
#
# It can be overridden via env using ${PN}_LIVE_REPO variable.
#
# Can be a whitespace-separated list or an array.
#
# Example:
# @CODE
# EGIT_REPO_URI="https://a/b.git https://c/d.git"
# @CODE

# @ECLASS-VARIABLE: EVCS_OFFLINE
# @DEFAULT_UNSET
# @DESCRIPTION:
# If non-empty, this variable prevents any online operations.

# @ECLASS-VARIABLE: EVCS_UMASK
# @DEFAULT_UNSET
# @DESCRIPTION:
# Set this variable to a custom umask. This is intended to be set by
# users. By setting this to something like 002, it can make life easier
# for people who do development as non-root (but are in the portage
# group), and then switch over to building with FEATURES=userpriv.
# Or vice-versa. Shouldn't be a security issue here as anyone who has
# portage group write access already can screw the system over in more
# creative ways.

# @ECLASS-VARIABLE: EGIT_BRANCH
# @DEFAULT_UNSET
# @DESCRIPTION:
# The branch name to check out. If unset, the upstream default (HEAD)
# will be used.
#
# It can be overridden via env using ${PN}_LIVE_BRANCH variable.

# @ECLASS-VARIABLE: EGIT_COMMIT
# @DEFAULT_UNSET
# @DESCRIPTION:
# The tag name or commit identifier to check out. If unset, newest
# commit from the branch will be used. Note that if set to a commit
# not on HEAD branch, EGIT_BRANCH needs to be set to a branch on which
# the commit is available.
#
# It can be overridden via env using ${PN}_LIVE_COMMIT variable.

# @ECLASS-VARIABLE: EGIT_COMMIT_DATE
# @DEFAULT_UNSET
# @DESCRIPTION:
# Attempt to check out the repository state for the specified timestamp.
# The date should be in format understood by 'git rev-list'. The commits
# on EGIT_BRANCH will be considered.
#
# The eclass will select the last commit with commit date preceding
# the specified date. When merge commits are found, only first parents
# will be considered in order to avoid switching into external branches
# (assuming that merges are done correctly). In other words, each merge
# will be considered alike a single commit with date corresponding
# to the merge commit date.
#
# It can be overridden via env using ${PN}_LIVE_COMMIT_DATE variable.

# @ECLASS-VARIABLE: EGIT_CHECKOUT_DIR
# @DESCRIPTION:
# The directory to check the git sources out to.
#
# EGIT_CHECKOUT_DIR=${WORKDIR}/${P}

# @ECLASS-VARIABLE: EGIT_SUBMODULES
# @DEFAULT_UNSET
# @DESCRIPTION:
# An array of inclusive and exclusive wildcards on submodule names,
# stating which submodules are fetched and checked out. Exclusions
# start with '-', and exclude previously matched submodules.
#
# If unset, all submodules are enabled. Empty list disables all
# submodules. In order to use an exclude-only list, start the array
# with '*'.
#
# Remember that wildcards need to be quoted in order to prevent filename
# expansion.
#
# Examples:
# @CODE
# # Disable all submodules
# EGIT_SUBMODULES=()
#
# # Include only foo and bar
# EGIT_SUBMODULES=( foo bar )
#
# # Use all submodules except for test-* but include test-lib
# EGIT_SUBMODULES=( '*' '-test-*' test-lib )
# @CODE

# @FUNCTION: _git-r3_env_setup
# @INTERNAL
# @DESCRIPTION:
# Set the eclass variables as necessary for operation. This can involve
# setting EGIT_* to defaults or ${PN}_LIVE_* variables.
_git-r3_env_setup() {
	debug-print-function ${FUNCNAME} "$@"

	# check the clone type
	case "${EGIT_CLONE_TYPE}" in
		mirror|single+tags|single|shallow)
			;;
		*)
			die "Invalid EGIT_CLONE_TYPE=${EGIT_CLONE_TYPE}"
	esac
	case "${EGIT_MIN_CLONE_TYPE}" in
		shallow)
			;;
		single)
			if [[ ${EGIT_CLONE_TYPE} == shallow ]]; then
				einfo "git-r3: ebuild needs to be cloned in '\e[1msingle\e[22m' mode, adjusting"
				EGIT_CLONE_TYPE=single
			fi
			;;
		single+tags)
			if [[ ${EGIT_CLONE_TYPE} == shallow || ${EGIT_CLONE_TYPE} == single ]]; then
				einfo "git-r3: ebuild needs to be cloned in '\e[1msingle+tags\e[22m' mode, adjusting"
				EGIT_CLONE_TYPE=single+tags
			fi
			;;
		mirror)
			if [[ ${EGIT_CLONE_TYPE} != mirror ]]; then
				einfo "git-r3: ebuild needs to be cloned in '\e[1mmirror\e[22m' mode, adjusting"
				EGIT_CLONE_TYPE=mirror
			fi
			;;
		*)
			die "Invalid EGIT_MIN_CLONE_TYPE=${EGIT_MIN_CLONE_TYPE}"
	esac

	if [[ ${EGIT_SUBMODULES[@]+1} && $(declare -p EGIT_SUBMODULES) != "declare -a"* ]]
	then
		die 'EGIT_SUBMODULES must be an array.'
	fi

	local esc_pn livevar
	esc_pn=${PN//[-+]/_}
	[[ ${esc_pn} == [0-9]* ]] && esc_pn=_${esc_pn}

	livevar=${esc_pn}_LIVE_REPO
	EGIT_REPO_URI=${!livevar-${EGIT_REPO_URI}}
	[[ ${!livevar} ]] \
		&& ewarn "Using ${livevar}, no support will be provided"

	livevar=${esc_pn}_LIVE_BRANCH
	EGIT_BRANCH=${!livevar-${EGIT_BRANCH}}
	[[ ${!livevar} ]] \
		&& ewarn "Using ${livevar}, no support will be provided"

	livevar=${esc_pn}_LIVE_COMMIT
	EGIT_COMMIT=${!livevar-${EGIT_COMMIT}}
	[[ ${!livevar} ]] \
		&& ewarn "Using ${livevar}, no support will be provided"

	livevar=${esc_pn}_LIVE_COMMIT_DATE
	EGIT_COMMIT_DATE=${!livevar-${EGIT_COMMIT_DATE}}
	[[ ${!livevar} ]] \
		&& ewarn "Using ${livevar}, no support will be provided"

	if [[ ${EGIT_COMMIT} && ${EGIT_COMMIT_DATE} ]]; then
		die "EGIT_COMMIT and EGIT_COMMIT_DATE can not be specified simultaneously"
	fi

	# Migration helpers. Remove them when git-2 is removed.

	if [[ ${EGIT_SOURCEDIR} ]]; then
		eerror "EGIT_SOURCEDIR has been replaced by EGIT_CHECKOUT_DIR. While updating"
		eerror "your ebuild, please check whether the variable is necessary at all"
		eerror "since the default has been changed from \${S} to \${WORKDIR}/\${P}."
		eerror "Therefore, proper setting of S may be sufficient."
		die "EGIT_SOURCEDIR has been replaced by EGIT_CHECKOUT_DIR."
	fi

	if [[ ${EGIT_MASTER} ]]; then
		eerror "EGIT_MASTER has been removed. Instead, the upstream default (HEAD)"
		eerror "is used by the eclass. Please remove the assignment or use EGIT_BRANCH"
		eerror "as necessary."
		die "EGIT_MASTER has been removed."
	fi

	if [[ ${EGIT_HAS_SUBMODULES} ]]; then
		eerror "EGIT_HAS_SUBMODULES has been removed. The eclass no longer needs"
		eerror "to switch the clone type in order to support submodules and therefore"
		eerror "submodules are detected and fetched automatically. If you need to"
		eerror "disable or filter submodules, see EGIT_SUBMODULES."
		die "EGIT_HAS_SUBMODULES is no longer necessary."
	fi

	if [[ ${EGIT_PROJECT} ]]; then
		eerror "EGIT_PROJECT has been removed. Instead, the eclass determines"
		eerror "the local clone path using path in canonical EGIT_REPO_URI."
		eerror "If the current algorithm causes issues for you, please report a bug."
		die "EGIT_PROJECT is no longer necessary."
	fi

	if [[ ${EGIT_BOOTSTRAP} ]]; then
		eerror "EGIT_BOOTSTRAP has been removed. Please create proper src_prepare()"
		eerror "instead."
		die "EGIT_BOOTSTRAP has been removed."
	fi

	if [[ ${EGIT_NOUNPACK} ]]; then
		eerror "EGIT_NOUNPACK has been removed. The eclass no longer calls default"
		eerror "unpack function. If necessary, please declare proper src_unpack()."
		die "EGIT_NOUNPACK has been removed."
	fi
}

# @FUNCTION: _git-r3_set_gitdir
# @USAGE: <repo-uri>
# @INTERNAL
# @DESCRIPTION:
# Obtain the local repository path and set it as GIT_DIR. Creates
# a new repository if necessary.
#
# <repo-uri> may be used to compose the path. It should therefore be
# a canonical URI to the repository.
_git-r3_set_gitdir() {
	debug-print-function ${FUNCNAME} "$@"

	local repo_name=${1#*://*/}

	# strip the trailing slash
	repo_name=${repo_name%/}

	# strip common prefixes to make paths more likely to match
	# e.g. git://X/Y.git vs https://X/git/Y.git
	# (but just one of the prefixes)
	case "${repo_name}" in
		# gnome.org... who else?
		browse/*) repo_name=${repo_name#browse/};;
		# cgit can proxy requests to git
		cgit/*) repo_name=${repo_name#cgit/};;
		# pretty common
		git/*) repo_name=${repo_name#git/};;
		# gentoo.org
		gitroot/*) repo_name=${repo_name#gitroot/};;
		# sourceforge
		p/*) repo_name=${repo_name#p/};;
		# kernel.org
		pub/scm/*) repo_name=${repo_name#pub/scm/};;
	esac
	# ensure a .git suffix, same reason
	repo_name=${repo_name%.git}.git
	# now replace all the slashes
	repo_name=${repo_name//\//_}

	local distdir=${PORTAGE_ACTUAL_DISTDIR:-${DISTDIR}}
	: ${EGIT3_STORE_DIR:=${distdir}/git3-src}

	GIT_DIR=${EGIT3_STORE_DIR}/${repo_name}

	if [[ ! -d ${EGIT3_STORE_DIR} && ! ${EVCS_OFFLINE} ]]; then
		(
			addwrite /
			mkdir -p "${EGIT3_STORE_DIR}"
		) || die "Unable to create ${EGIT3_STORE_DIR}"
	fi

	addwrite "${EGIT3_STORE_DIR}"
	if [[ ! -d ${GIT_DIR} ]]; then
		if [[ ${EVCS_OFFLINE} ]]; then
			eerror "A clone of the following repository is required to proceed:"
			eerror "  ${1}"
			eerror "However, networking activity has been disabled using EVCS_OFFLINE and there"
			eerror "is no local clone available."
			die "No local clone of ${1}. Unable to proceed with EVCS_OFFLINE."
		fi

		local saved_umask
		if [[ ${EVCS_UMASK} ]]; then
			saved_umask=$(umask)
			umask "${EVCS_UMASK}" || die "Bad options to umask: ${EVCS_UMASK}"
		fi
		mkdir "${GIT_DIR}" || die
		git init --bare || die
		if [[ ${saved_umask} ]]; then
			umask "${saved_umask}" || die
		fi
	fi
}

# @FUNCTION: _git-r3_set_submodules
# @USAGE: <file-contents>
# @INTERNAL
# @DESCRIPTION:
# Parse .gitmodules contents passed as <file-contents>
# as in "$(cat .gitmodules)"). Composes a 'submodules' array that
# contains in order (name, URL, path) for each submodule.
_git-r3_set_submodules() {
	debug-print-function ${FUNCNAME} "$@"

	local data=${1}

	# ( name url path ... )
	submodules=()

	local l
	while read l; do
		# submodule.<path>.path=<path>
		# submodule.<path>.url=<url>
		[[ ${l} == submodule.*.url=* ]] || continue

		l=${l#submodule.}
		local subname=${l%%.url=*}

		# filter out on EGIT_SUBMODULES
		if declare -p EGIT_SUBMODULES &>/dev/null; then
			local p l_res res=
			for p in "${EGIT_SUBMODULES[@]}"; do
				if [[ ${p} == -* ]]; then
					p=${p#-}
					l_res=
				else
					l_res=1
				fi

				[[ ${subname} == ${p} ]] && res=${l_res}
			done

			if [[ ! ${res} ]]; then
				einfo "Skipping submodule \e[1m${subname}\e[22m"
				continue
			fi
		fi

		# skip modules that have 'update = none', bug #487262.
		local upd=$(echo "${data}" | git config -f /dev/fd/0 \
			submodule."${subname}".update)
		[[ ${upd} == none ]] && continue

		# https://github.com/git/git/blob/master/refs.c#L31
		# we are more restrictive than git itself but that should not
		# cause any issues, #572312, #606950
		# TODO: check escaped names for collisions
		local enc_subname=${subname//[^a-zA-Z0-9-]/_}

		submodules+=(
			"${enc_subname}"
			"$(echo "${data}" | git config -f /dev/fd/0 \
				submodule."${subname}".url || die)"
			"$(echo "${data}" | git config -f /dev/fd/0 \
				submodule."${subname}".path || die)"
		)
	done < <(echo "${data}" | git config -f /dev/fd/0 -l || die)
}

# @FUNCTION: _git-r3_set_subrepos
# @USAGE: <submodule-uri> <parent-repo-uri>...
# @INTERNAL
# @DESCRIPTION:
# Create 'subrepos' array containing absolute (canonical) submodule URIs
# for the given <submodule-uri>. If the URI is relative, URIs will be
# constructed using all <parent-repo-uri>s. Otherwise, this single URI
# will be placed in the array.
_git-r3_set_subrepos() {
	debug-print-function ${FUNCNAME} "$@"

	local suburl=${1}
	subrepos=( "${@:2}" )

	if [[ ${suburl} == ./* || ${suburl} == ../* ]]; then
		# drop all possible trailing slashes for consistency
		subrepos=( "${subrepos[@]%%/}" )

		while true; do
			if [[ ${suburl} == ./* ]]; then
				suburl=${suburl:2}
			elif [[ ${suburl} == ../* ]]; then
				suburl=${suburl:3}

				# XXX: correctness checking

				# drop the last path component
				subrepos=( "${subrepos[@]%/*}" )
				# and then the trailing slashes, again
				subrepos=( "${subrepos[@]%%/}" )
			else
				break
			fi
		done

		# append the preprocessed path to the preprocessed URIs
		subrepos=( "${subrepos[@]/%//${suburl}}")
	else
		subrepos=( "${suburl}" )
	fi
}


# @FUNCTION: _git-r3_is_local_repo
# @USAGE: <repo-uri>
# @INTERNAL
# @DESCRIPTION:
# Determine whether the given URI specifies a local (on-disk)
# repository.
_git-r3_is_local_repo() {
	debug-print-function ${FUNCNAME} "$@"

	local uri=${1}

	[[ ${uri} == file://* || ${uri} == /* ]]
}

# @FUNCTION: git-r3_fetch
# @USAGE: [<repo-uri> [<remote-ref> [<local-id> [<commit-date>]]]]
# @DESCRIPTION:
# Fetch new commits to the local clone of repository.
#
# <repo-uri> specifies the repository URIs to fetch from, as a space-
# -separated list. The first URI will be used as repository group
# identifier and therefore must be used consistently. When not
# specified, defaults to ${EGIT_REPO_URI}.
#
# <remote-ref> specifies the remote ref or commit id to fetch.
# It is preferred to use 'refs/heads/<branch-name>' for branches
# and 'refs/tags/<tag-name>' for tags. Other options are 'HEAD'
# for upstream default branch and hexadecimal commit SHA1. Defaults
# to the first of EGIT_COMMIT, EGIT_BRANCH or literal 'HEAD' that
# is set to a non-null value.
#
# <local-id> specifies the local branch identifier that will be used to
# locally store the fetch result. It should be unique to multiple
# fetches within the repository that can be performed at the same time
# (including parallel merges). It defaults to ${CATEGORY}/${PN}/${SLOT%/*}.
# This default should be fine unless you are fetching multiple trees
# from the same repository in the same ebuild.
#
# <commit-id> requests attempting to use repository state as of specific
# date. For more details, see EGIT_COMMIT_DATE.
#
# The fetch operation will affect the EGIT_STORE only. It will not touch
# the working copy, nor export any environment variables.
# If the repository contains submodules, they will be fetched
# recursively.
git-r3_fetch() {
	debug-print-function ${FUNCNAME} "$@"

	# process repos first since we create repo_name from it
	local repos
	if [[ ${1} ]]; then
		repos=( ${1} )
	elif [[ $(declare -p EGIT_REPO_URI) == "declare -a"* ]]; then
		repos=( "${EGIT_REPO_URI[@]}" )
	else
		repos=( ${EGIT_REPO_URI} )
	fi

	[[ ${repos[@]} ]] || die "No URI provided and EGIT_REPO_URI unset"

	local r
	for r in "${repos[@]}"; do
		if [[ ${r} == git:* || ${r} == http:* ]]; then
			ewarn "git-r3: ${r%%:*} protocol is completely unsecure and may render the ebuild"
			ewarn "easily susceptible to MITM attacks (even if used only as fallback). Please"
			ewarn "use https instead."
			ewarn "[URI: ${r}]"
		fi
	done

	local -x GIT_DIR
	_git-r3_set_gitdir "${repos[0]}"

	# prepend the local mirror if applicable
	if [[ ${EGIT_MIRROR_URI} ]]; then
		repos=(
			"${EGIT_MIRROR_URI%/}/${GIT_DIR##*/}"
			"${repos[@]}"
		)
	fi

	# get the default values for the common variables and override them
	local branch_name=${EGIT_BRANCH}
	local commit_id=${2:-${EGIT_COMMIT}}
	local commit_date=${4:-${EGIT_COMMIT_DATE}}

	# support new override API for EAPI 6+
	if ! has "${EAPI:-0}" 0 1 2 3 4 5; then
		# get the name and do some more processing:
		# 1) kill .git suffix,
		# 2) underscore (remaining) non-variable characters,
		# 3) add preceding underscore if it starts with a digit,
		# 4) uppercase.
		local override_name=${GIT_DIR##*/}
		override_name=${override_name%.git}
		override_name=${override_name//[^a-zA-Z0-9_]/_}
		override_name=${override_name^^}

		local varmap=(
			REPO:repos
			BRANCH:branch_name
			COMMIT:commit_id
			COMMIT_DATE:commit_date
		)

		local localvar livevar live_warn=
		for localvar in "${varmap[@]}"; do
			livevar=EGIT_OVERRIDE_${localvar%:*}_${override_name}
			localvar=${localvar#*:}

			if [[ -n ${!livevar} ]]; then
				[[ ${localvar} == repos ]] && repos=()
				live_warn=1
				ewarn "Using ${livevar}=${!livevar}"
				declare "${localvar}=${!livevar}"
			fi
		done

		if [[ ${live_warn} ]]; then
			ewarn "No support will be provided."
		fi
	fi

	# set final variables after applying overrides
	local branch=${branch_name:+refs/heads/${branch_name}}
	local remote_ref=${commit_id:-${branch:-HEAD}}
	local local_id=${3:-${CATEGORY}/${PN}/${SLOT%/*}}
	local local_ref=refs/git-r3/${local_id}/__main__

	# try to fetch from the remote
	local success saved_umask
	if [[ ${EVCS_UMASK} ]]; then
		saved_umask=$(umask)
		umask "${EVCS_UMASK}" || die "Bad options to umask: ${EVCS_UMASK}"
	fi
	for r in "${repos[@]}"; do
		if [[ ! ${EVCS_OFFLINE} ]]; then
			einfo "Fetching \e[1m${r}\e[22m ..."

			local fetch_command=( git fetch "${r}" )
			local clone_type=${EGIT_CLONE_TYPE}

			if [[ ${clone_type} == mirror ]]; then
				fetch_command+=(
					--prune
					# mirror the remote branches as local branches
					"+refs/heads/*:refs/heads/*"
					# pull tags explicitly in order to prune them properly
					"+refs/tags/*:refs/tags/*"
					# notes in case something needs them
					"+refs/notes/*:refs/notes/*"
					# and HEAD in case we need the default branch
					# (we keep it in refs/git-r3 since otherwise --prune interferes)
					"+HEAD:refs/git-r3/HEAD"
				)
			else # single or shallow
				local fetch_l fetch_r

				if [[ ${remote_ref} == HEAD ]]; then
					# HEAD
					fetch_l=HEAD
				elif [[ ${remote_ref} == refs/* ]]; then
					# regular branch, tag or some other explicit ref
					fetch_l=${remote_ref}
				else
					# tag or commit id...
					# let ls-remote figure it out
					local tagref=$(git ls-remote "${r}" "refs/tags/${remote_ref}")

					# if it was a tag, ls-remote obtained a hash
					if [[ ${tagref} ]]; then
						# tag
						fetch_l=refs/tags/${remote_ref}
					else
						# commit id
						# so we need to fetch the whole branch
						if [[ ${branch} ]]; then
							fetch_l=${branch}
						else
							fetch_l=HEAD
						fi

						# fetching by commit in shallow mode? can't do.
						if [[ ${clone_type} == shallow ]]; then
							clone_type=single
						fi
					fi
				fi

				# checkout by date does not make sense in shallow mode
				if [[ ${commit_date} && ${clone_type} == shallow ]]; then
					clone_type=single
				fi

				if [[ ${fetch_l} == HEAD ]]; then
					fetch_r=refs/git-r3/HEAD
				else
					fetch_r=${fetch_l}
				fi

				fetch_command+=(
					"+${fetch_l}:${fetch_r}"
				)

				if [[ ${clone_type} == single+tags ]]; then
					fetch_command+=(
						# pull tags explicitly as requested
						"+refs/tags/*:refs/tags/*"
					)
				fi
			fi

			if [[ ${clone_type} == shallow ]]; then
				if _git-r3_is_local_repo; then
					# '--depth 1' causes sandbox violations with local repos
					# bug #491260
					clone_type=single
				elif [[ ! $(git rev-parse --quiet --verify "${fetch_r}") ]]
				then
					# use '--depth 1' when fetching a new branch
					fetch_command+=( --depth 1 )
				fi
			else # non-shallow mode
				if [[ -f ${GIT_DIR}/shallow ]]; then
					fetch_command+=( --unshallow )
				fi
			fi

			set -- "${fetch_command[@]}"
			echo "${@}" >&2
			"${@}" || continue

			if [[ ${clone_type} == mirror || ${fetch_l} == HEAD ]]; then
				# update our HEAD to match our remote HEAD ref
				git symbolic-ref HEAD refs/git-r3/HEAD \
						|| die "Unable to update HEAD"
			fi
		fi

		# now let's see what the user wants from us
		if [[ ${commit_date} ]]; then
			local dated_commit_id=$(
				git rev-list --first-parent --before="${commit_date}" \
					-n 1 "${remote_ref}"
			)
			if [[ ${?} -ne 0 ]]; then
				die "Listing ${remote_ref} failed (wrong ref?)."
			elif [[ ! ${dated_commit_id} ]]; then
				die "Unable to find commit for date ${commit_date}."
			else
				set -- git update-ref --no-deref "${local_ref}" "${dated_commit_id}"
			fi
		else
			local full_remote_ref=$(
				git rev-parse --verify --symbolic-full-name "${remote_ref}"
			)

			if [[ ${full_remote_ref} ]]; then
				# when we are given a ref, create a symbolic ref
				# so that we preserve the actual argument
				set -- git symbolic-ref "${local_ref}" "${full_remote_ref}"
			else
				# otherwise, we were likely given a commit id
				set -- git update-ref --no-deref "${local_ref}" "${remote_ref}"
			fi
		fi

		echo "${@}" >&2
		if ! "${@}"; then
			if [[ ${EVCS_OFFLINE} ]]; then
				eerror "A clone of the following repository is required to proceed:"
				eerror "  ${r}"
				eerror "However, networking activity has been disabled using EVCS_OFFLINE and the local"
				eerror "clone does not have requested ref:"
				eerror "  ${remote_ref}"
				die "Local clone of ${r} does not have requested ref: ${remote_ref}. Unable to proceed with EVCS_OFFLINE."
			else
				die "Referencing ${remote_ref} failed (wrong ref?)."
			fi
		fi

		success=1
		break
	done
	if [[ ${saved_umask} ]]; then
		umask "${saved_umask}" || die
	fi
	[[ ${success} ]] || die "Unable to fetch from any of EGIT_REPO_URI"

	# submodules can reference commits in any branch
	# always use the 'mirror' mode to accomodate that, bug #503332
	local EGIT_CLONE_TYPE=mirror

	# recursively fetch submodules
	if git cat-file -e "${local_ref}":.gitmodules &>/dev/null; then
		local submodules
		_git-r3_set_submodules \
			"$(git cat-file -p "${local_ref}":.gitmodules || die)"

		while [[ ${submodules[@]} ]]; do
			local subname=${submodules[0]}
			local url=${submodules[1]}
			local path=${submodules[2]}

			# use only submodules for which path does exist
			# (this is in par with 'git submodule'), bug #551100
			# note: git cat-file does not work for submodules
			if [[ $(git ls-tree -d "${local_ref}" "${path}") ]]
			then
				local commit=$(git rev-parse "${local_ref}:${path}" || die)

				if [[ ! ${commit} ]]; then
					die "Unable to get commit id for submodule ${subname}"
				fi

				local subrepos
				_git-r3_set_subrepos "${url}" "${repos[@]}"

				git-r3_fetch "${subrepos[*]}" "${commit}" "${local_id}/${subname}"
			fi

			submodules=( "${submodules[@]:3}" ) # shift
		done
	fi
}

# @FUNCTION: git-r3_checkout
# @USAGE: [<repo-uri> [<checkout-path> [<local-id> [<checkout-paths>...]]]]
# @DESCRIPTION:
# Check the previously fetched tree to the working copy.
#
# <repo-uri> specifies the repository URIs, as a space-separated list.
# The first URI will be used as repository group identifier
# and therefore must be used consistently with git-r3_fetch.
# The remaining URIs are not used and therefore may be omitted.
# When not specified, defaults to ${EGIT_REPO_URI}.
#
# <checkout-path> specifies the path to place the checkout. It defaults
# to ${EGIT_CHECKOUT_DIR} if set, otherwise to ${WORKDIR}/${P}.
#
# <local-id> needs to specify the local identifier that was used
# for respective git-r3_fetch.
#
# If <checkout-paths> are specified, then the specified paths are passed
# to 'git checkout' to effect a partial checkout. Please note that such
# checkout will not cause the repository to switch branches,
# and submodules will be skipped at the moment. The submodules matching
# those paths might be checked out in a future version of the eclass.
#
# The checkout operation will write to the working copy, and export
# the repository state into the environment. If the repository contains
# submodules, they will be checked out recursively.
git-r3_checkout() {
	debug-print-function ${FUNCNAME} "$@"

	local repos
	if [[ ${1} ]]; then
		repos=( ${1} )
	elif [[ $(declare -p EGIT_REPO_URI) == "declare -a"* ]]; then
		repos=( "${EGIT_REPO_URI[@]}" )
	else
		repos=( ${EGIT_REPO_URI} )
	fi

	local out_dir=${2:-${EGIT_CHECKOUT_DIR:-${WORKDIR}/${P}}}
	local local_id=${3:-${CATEGORY}/${PN}/${SLOT%/*}}
	local checkout_paths=( "${@:4}" )

	local -x GIT_DIR
	_git-r3_set_gitdir "${repos[0]}"

	einfo "Checking out \e[1m${repos[0]}\e[22m to \e[1m${out_dir}\e[22m ..."

	if ! git cat-file -e refs/git-r3/"${local_id}"/__main__; then
		die "Logic error: no local clone of ${repos[0]}. git-r3_fetch not used?"
	fi
	local remote_ref=$(
		git symbolic-ref --quiet refs/git-r3/"${local_id}"/__main__
	)
	local new_commit_id=$(
		git rev-parse --verify refs/git-r3/"${local_id}"/__main__
	)

	git-r3_sub_checkout() {
		local orig_repo=${GIT_DIR}
		local -x GIT_DIR=${out_dir}/.git
		local -x GIT_WORK_TREE=${out_dir}

		mkdir -p "${out_dir}" || die

		# use git init+fetch instead of clone since the latter doesn't like
		# non-empty directories.

		git init --quiet || die
		# setup 'alternates' to avoid copying objects
		echo "${orig_repo}/objects" > "${GIT_DIR}"/objects/info/alternates || die
		# now copy the refs
		cp -R "${orig_repo}"/refs/* "${GIT_DIR}"/refs/ || die
		if [[ -f ${orig_repo}/packed-refs ]]; then
			cp "${orig_repo}"/packed-refs "${GIT_DIR}"/packed-refs || die
		fi

		# (no need to copy HEAD, we will set it via checkout)

		if [[ -f ${orig_repo}/shallow ]]; then
			cp "${orig_repo}"/shallow "${GIT_DIR}"/ || die
		fi

		set -- git checkout --quiet
		if [[ ${remote_ref} ]]; then
			set -- "${@}" "${remote_ref#refs/heads/}"
		else
			set -- "${@}" "${new_commit_id}"
		fi
		if [[ ${checkout_paths[@]} ]]; then
			set -- "${@}" -- "${checkout_paths[@]}"
		fi
		echo "${@}" >&2
		"${@}" || die "git checkout ${remote_ref:-${new_commit_id}} failed"
	}
	git-r3_sub_checkout
	unset -f git-r3_sub_checkout

	local old_commit_id=$(
		git rev-parse --quiet --verify refs/git-r3/"${local_id}"/__old__
	)
	if [[ ! ${old_commit_id} ]]; then
		echo "GIT NEW branch -->"
		echo "   repository:               ${repos[0]}"
		echo "   at the commit:            ${new_commit_id}"
	else
		# diff against previous revision
		echo "GIT update -->"
		echo "   repository:               ${repos[0]}"
		# write out message based on the revisions
		if [[ "${old_commit_id}" != "${new_commit_id}" ]]; then
			echo "   updating from commit:     ${old_commit_id}"
			echo "   to commit:                ${new_commit_id}"

			set -- git --no-pager diff --stat \
				${old_commit_id}..${new_commit_id}
			if [[ ${checkout_paths[@]} ]]; then
				set -- "${@}" -- "${checkout_paths[@]}"
			fi
			"${@}"
		else
			echo "   at the commit:            ${new_commit_id}"
		fi
	fi
	git update-ref --no-deref refs/git-r3/"${local_id}"/{__old__,__main__} || die

	# recursively checkout submodules
	if [[ -f ${out_dir}/.gitmodules && ! ${checkout_paths} ]]; then
		local submodules
		_git-r3_set_submodules \
			"$(<"${out_dir}"/.gitmodules)"

		while [[ ${submodules[@]} ]]; do
			local subname=${submodules[0]}
			local url=${submodules[1]}
			local path=${submodules[2]}

			# use only submodules for which path does exist
			# (this is in par with 'git submodule'), bug #551100
			if [[ -d ${out_dir}/${path} ]]; then
				local subrepos
				_git-r3_set_subrepos "${url}" "${repos[@]}"

				git-r3_checkout "${subrepos[*]}" "${out_dir}/${path}" \
					"${local_id}/${subname}"
			fi

			submodules=( "${submodules[@]:3}" ) # shift
		done
	fi

	# keep this *after* submodules
	export EGIT_DIR=${GIT_DIR}
	export EGIT_VERSION=${new_commit_id}
}

# @FUNCTION: git-r3_peek_remote_ref
# @USAGE: [<repo-uri> [<remote-ref>]]
# @DESCRIPTION:
# Peek the reference in the remote repository and print the matching
# (newest) commit SHA1.
#
# <repo-uri> specifies the repository URIs to fetch from, as a space-
# -separated list. When not specified, defaults to ${EGIT_REPO_URI}.
#
# <remote-ref> specifies the remote ref to peek.  It is preferred to use
# 'refs/heads/<branch-name>' for branches and 'refs/tags/<tag-name>'
# for tags. Alternatively, 'HEAD' may be used for upstream default
# branch. Defaults to the first of EGIT_COMMIT, EGIT_BRANCH or literal
# 'HEAD' that is set to a non-null value.
#
# The operation will be done purely on the remote, without using local
# storage. If commit SHA1 is provided as <remote-ref>, the function will
# fail due to limitations of git protocol.
#
# On success, the function returns 0 and writes hexadecimal commit SHA1
# to stdout. On failure, the function returns 1.
git-r3_peek_remote_ref() {
	debug-print-function ${FUNCNAME} "$@"

	local repos
	if [[ ${1} ]]; then
		repos=( ${1} )
	elif [[ $(declare -p EGIT_REPO_URI) == "declare -a"* ]]; then
		repos=( "${EGIT_REPO_URI[@]}" )
	else
		repos=( ${EGIT_REPO_URI} )
	fi

	local branch=${EGIT_BRANCH:+refs/heads/${EGIT_BRANCH}}
	local remote_ref=${2:-${EGIT_COMMIT:-${branch:-HEAD}}}

	[[ ${repos[@]} ]] || die "No URI provided and EGIT_REPO_URI unset"

	local r success
	for r in "${repos[@]}"; do
		einfo "Peeking \e[1m${remote_ref}\e[22m on \e[1m${r}\e[22m ..." >&2

		local lookup_ref
		if [[ ${remote_ref} == refs/* || ${remote_ref} == HEAD ]]
		then
			lookup_ref=${remote_ref}
		else
			# ls-remote by commit is going to fail anyway,
			# so we may as well pass refs/tags/ABCDEF...
			lookup_ref=refs/tags/${remote_ref}
		fi

		# split on whitespace
		local ref=(
			$(git ls-remote "${r}" "${lookup_ref}")
		)

		if [[ ${ref[0]} ]]; then
			echo "${ref[0]}"
			return 0
		fi
	done

	return 1
}

git-r3_src_fetch() {
	debug-print-function ${FUNCNAME} "$@"

	if [[ ! ${EGIT3_STORE_DIR} && ${EGIT_STORE_DIR} ]]; then
		ewarn "You have set EGIT_STORE_DIR but not EGIT3_STORE_DIR. Please consider"
		ewarn "setting EGIT3_STORE_DIR for git-r3.eclass. It is recommended to use"
		ewarn "a different directory than EGIT_STORE_DIR to ease removing old clones"
		ewarn "when git-2 eclass becomes deprecated."
	fi

	_git-r3_env_setup
	git-r3_fetch
}

git-r3_src_unpack() {
	debug-print-function ${FUNCNAME} "$@"

	_git-r3_env_setup
	git-r3_src_fetch
	git-r3_checkout
}

# https://bugs.gentoo.org/show_bug.cgi?id=482666
git-r3_pkg_needrebuild() {
	debug-print-function ${FUNCNAME} "$@"

	local new_commit_id=$(git-r3_peek_remote_ref)
	[[ ${new_commit_id} && ${EGIT_VERSION} ]] || die "Lookup failed"

	if [[ ${EGIT_VERSION} != ${new_commit_id} ]]; then
		einfo "Update from \e[1m${EGIT_VERSION}\e[22m to \e[1m${new_commit_id}\e[22m"
	else
		einfo "Local and remote at \e[1m${EGIT_VERSION}\e[22m"
	fi

	[[ ${EGIT_VERSION} != ${new_commit_id} ]]
}

# 'export' locally until this gets into EAPI
pkg_needrebuild() { git-r3_pkg_needrebuild; }

_GIT_R3=1
fi