GNU Stow -> hstow, and follow-up tidying & simplifications

1 files changed, 172 insertions, 0 deletions

diff --git a/bin/hstow b/bin/hstow
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+++ b/bin/hstow
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+#!/bin/sh
+
+# hstow -- POSIX sh minimal reimplementation of GNU Stow for dotfiles
+#
+# Copyright (C) 2022  Sean Whitton <spwhitton@spwhitton.name>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or (at
+# your option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# The point of this script is to obtain minimally functional dotfiles
+# handling in one's home directory on even machines that lack a Perl
+# interpreter.  As such, many of GNU Stow's more advanced features are
+# not reimplemented.  Git depends on Perl, for now, but my two methods
+# for deploying my dotfiles to remote machines -- my INSINUATE-DOTFILES
+# Consfigurator property and 'insinuate-dotfiles' shell script -- do not
+# depend on having Git on the remote side.  See also 'bstraph' script.
+#
+# We completely skip filenames containing control characters, including
+# newline and tab, as POSIX find(1) lacks -print0, and it's unlikely
+# you'd need to stow any such files.
+# Technique from <https://dwheeler.com/essays/filenames-in-shell.html>.
+
+set -efu
+IFS="$(printf '\n\t')"
+export LC_ALL=C
+tab="$(printf '\t')"
+cchars="$(printf '*[\001-\037\177]*')"
+
+if ! command -v readlink >/dev/null; then
+    readlink () {
+	# Safe parse of ls(1) output given its POSIX specification.
+	ls -ld "$1" | tr -s ' ' \
+	    | cut -d' ' -f9- | cut -c$((4 + $(echo "$1" | wc -c)))-
+    }
+fi
+
+read_globs_file () {
+    if [ -e "$DIR/$1" ]; then
+	while read -r line; do
+	    printf "|./%s" "$line"
+	done <"$DIR/$1" | cut -c2-
+    fi
+}
+
+dir_contents () {
+    ( cd "$1"; find . ! -name . ! -name "$cchars" )
+}
+
+fail () {
+    echo >&2 "hstow: $*"
+    exit 127
+}
+
+usage () {
+    fail "usage: hstow stow|unstow|restow|adopt DIRECTORY"
+}
+
+stow () {
+    cd "$DIR"
+    [ -d "$HOME/.STOW" ] || mkdir "$HOME/.STOW"
+    [ -f "$HOME/.STOW/.stow" ] || touch "$HOME/.STOW/.stow"
+    [ -h "$HOME/.STOW/$NAME" ] \
+	|| ( cd "$HOME/.STOW"; ln -s "$DIR" "$NAME" )
+    conflicts=
+    ignores="$(read_globs_file .hstow-local-ignore)"
+
+    # Files that (i) always/often have their symlinks replaced with
+    # regular files when applications access them; and (ii) we don't
+    # ever want to edit the copy under $DIR directly, but only via the
+    # link/copy under $HOME.
+    $always_adopt || adoptions="$(read_globs_file .hstow-always-adopt)"
+
+    for file in $(find . ! -name . ! -type d ! -name "$cchars" \
+		       ! -name .gitignore \
+		       ! -name .hstow-local-ignore \
+		       ! -name .hstow-always-adopt \
+		      | grep -v '^\./\.git/'); do
+	file_dir="$(dirname $file)"
+	if [ -n "$ignores" ]; then
+	    eval case "'$file'"     in "${ignores})" continue ";;" esac
+	    eval case "'$file_dir'" in "${ignores})" continue ";;" esac
+	fi
+
+	rel="$(echo $file | sed -E 's#/dot[-.]([^/]+)#/.\1#g; s#^\./##')"
+	dotdotslashes="$(echo $rel | sed -E 's#[^/]*$##; s#[^/]+#..#g')"
+	target="${dotdotslashes}.STOW/$NAME/$rel"
+	link="$HOME/$rel"
+	link_target=
+	[ -h "$link" ] && link_target="$(readlink $link)"
+
+	[ "$target" = "$link_target" ] && continue
+
+	if [ ! -h "$link" -a ! -h "$file" -a -f "$link" ]; then
+	    if $always_adopt \
+		    || ( [ -n "$adoptions" ] \
+			     && eval case "'$file'" in \
+				     "${adoptions})" exit 0 ";;" \
+				     "*)"            exit 1 ";;" \
+				     esac ); then
+		mv -f "$link" "$file"
+		ln -s "$target" "$link"
+	    else
+		conflicts="$conflicts${tab}$file"
+	    fi
+	elif [ -h "$link" ]; then
+	    # With at least GNU ln(1), passing -f, but not also -T, does not
+	    # replace an existing link in some cases.
+	    # -T is not POSIX, so we just remove any existing link first.
+	    rm "$link"
+	    ln -s "$target" "$link"
+	else
+	    mkdir -p "$HOME/$file_dir"
+	    ln -s "$target" "$link"
+	fi
+    done
+    [ -z "$conflicts" ] && return
+    echo >&2 "hstow: encountered conflicts:"
+    for conflict in $conflicts; do echo >&2 "  $conflict"; done
+    exit 127
+}
+
+unstow () {
+    cd "$HOME"
+    dir_pat="^.$(echo $DIR | cut -c$(echo $HOME | wc -c)-)/"
+    for file in $(find . -type l ! -name . ! -name "$cchars" \
+		      | grep -v "$dir_pat"); do
+	if readlink "$file" | grep -Eq '^(\.\./)*\.STOW/'"$NAME/"; then
+	    rm "$file"
+	    while true; do
+		file="$(dirname $file)"
+		[ "$file" = . ] && break
+		if [ -z "$(dir_contents $file)" ]; then
+		    rmdir "$file"
+		else
+		    break
+		fi
+	    done
+	fi
+    done
+    [ -e "$HOME/.STOW/$NAME" ] && rm "$HOME/.STOW/$NAME"
+    if [ -d "$HOME/.STOW" ] \
+	   && [ "$(dir_contents $HOME/.STOW)" = "./.stow" ]; then
+	rm "$HOME/.STOW/.stow"
+	rmdir "$HOME/.STOW"
+    fi
+}
+
+[ $# = 2 ] || usage
+[ -d "$2" ] || fail "$2 is not an existing directory"
+DIR="$(cd $2; pwd)"
+[ "$(echo $DIR | cut -c-$(($(echo $HOME | wc -c) - 1)))" = "$HOME" ] \
+    || fail "$DIR is not below $HOME"
+
+NAME="$(echo $DIR | tr / _)"
+always_adopt=false
+case "$1" in
+    'stow')   stow			;;
+    'unstow') unstow			;;
+    'restow') unstow; stow		;;
+    'adopt')  always_adopt=true; stow	;;
+    *)        usage                     ;;
+esac