initial commit.

LICENSE

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+The MIT License (MIT)
+
+Copyright 2020 "yafox"
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README

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+lmr
+====
+
+pronounced "lemur."  an abbreviation of "link merge."
+
+merges the contents of one directory into another using filesystem links.
+
+can reverse a merge as long as the contents of the source directory have
+not changed since the merge was completed and no files were overwritten
+during the merge.  if files were removed from the source directory, "dangling"
+symlinks will be left behind.
+
+lmr exists for much the same reason as gnu stow, but has significantly fewer
+features and operates more like a recursive `ln` than a simplified `stow`.
+
+lmr is implemented as a single, 80 SLOC long, POSIX-compliant shell script.
+
+usage: lmr [-c] [-f] [-s] [-t|-u] [--] <src> <dest>
+
+options:
+    -c: check for file conflicts.  link nothing.
+    -f: force link creation, even if it overwrites files.
+    -s: use symlinks instead of hard links.
+    -t: exit if it seems a lmr has already been done between <src> and <dest>.
+    -u: try to undo a previous lmr from <src> to <dest>.
+    --: optional "end of flags" marker.

lmr.sh

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+#!/bin/sh -e
+
+[ -n "$1" ] || { \
+echo "
+usage: $(basename $0) [-c] [-f] [-s] [-t|-u] [--] <src> <dest>
+
+options:
+    -c: check for file conflicts.  link nothing.
+    -f: force link creation, even if it overwrites files.
+    -s: use symlinks instead of hard links.
+    -t: exit if it seems a lmr has already been done between <src> and <dest>.
+    -u: try to undo a previous lmr from <src> to <dest>.
+    --: optional "end of flags" marker.
+" && exit 0; }
+
+# if this is running on an interactive terminal (as opposed to in a script), if
+# tput is installed, and if tput knows some color codes, then set color values.
+if [ -t 1 ] && [ "$(tput colors 2>/dev/null || echo 0)" -ge 8 ]; then
+    _clr="$(tput sgr0)"
+    _blu="$(tput setaf 6)"
+    _ylw="$(tput setaf 3)"
+    _red="$(tput setaf 1)"
+fi
+log() { echo "$_blu[LOG]$_clr $@"; }
+wrn() { echo "$_ylw[WRN]$_clr $@" >&2; }
+err() { echo "$_red[ERR]$_clr $@" >&2; exit 1; }
+
+# -e checks if a file exists, but also dereferences symlinks and returns false
+# if the link's target does not exist.  -L returns true if the file exists and
+# is a symlink; it does not dereference symlinks.
+exists() { [ -e "$1" ] || [ -L "$1" ]; }
+
+linked() {
+    # -ef returns true if the files exist and refer to the same file.
+    { [ -z "$soft" ] && [ "$1" -ef "$2" ]; } \
+    || [ "$1" = "$(readlink "$2" 2> /dev/null)" ] \
+    || return 1
+}
+export linked
+
+while [ "$1" != "${1#-}" ]; do
+    case "$1" in
+        -c) check="yes";;
+        -f) flags="$flags -f";;
+        -s) soft="yes";;
+        -t) test="yes";;
+        -u) undo="yes";;
+        --) break;;
+        *) err "unrecognized option '$1'";;
+    esac
+    shift
+done
+
+src="$1"
+dest="$2"
+
+[ -d "$1" ] || err "not a directory: $1"
+[ -d "$2" ] || err "not a directory: $2"
+
+if [ -z "$undo" ]; then
+    [ -z "$soft" ] && flags="$flags -P" || flags="$flags -s"
+
+    find "$src" -type d ! -path "$src" -exec sh -c \
+    "mkdir -p \$(echo \"$dest/\${0#$src}\" | tr -s '/')" {} \;
+
+    find "$src" \( -type f -o -type l \) | while read lnsrc; do
+        lndest="$dest/${lnsrc#$src}"
+
+        if [ -z "$test" ]; then
+            linked "$lnsrc" "$lndest" \
+            && exit 0 \
+            || exit 1
+
+        elif [ -z "$check" ]; then
+            {  ! exists "$lndest"; } \
+            || linked "$lnsrc" "$lndest" \
+            || wrn "conflict: ${lnsrc#$src}"
+
+        else
+            ln$flags "$lnsrc" "$lndest"
+        fi
+    done
+
+else
+    # delete all files in the destination directory which are either soft or
+    # hard links (depending on whether the -s flag was set) to files in the
+    # source directory.
+    find "$src" \( -type f -o -type l \) | while read lnsrc; do
+        lndest="$dest/${lnsrc#$src}"
+
+        exists "$lndest" || continue;
+
+        # only remove the file in the "destination" directory if it is a hard or
+        # a soft link to the source file.
+        { ! linked "$lnsrc" "$lndest"; } || rm "$lndest"
+    done
+
+    # recursively remove any empty directories in the destination directory
+    # which also exist in the source directory.  while no guarantee that these
+    # were created by a previous lmr operation, this seems a decent heuristic.
+    # reverse-sorting by path length to ensure "leaves" are processed first.
+    find "$src" -type d ! -path "$src" \
+    | awk '{ print length() "\t" $0 | "sort -nr" }' \
+    | cut -f2 \
+    | while read dir; do
+        destdir="$dest/${dir#$src}"
+
+        # avoid "directory not empty" errors below.
+        [ -d "$destdir" ] && [ -z "$(ls -A $destdir/)" ] || continue;
+
+        # rmdir will only delete empty directories.
+        # use it in case the line above fails to detect something.
+        rmdir "$destdir" || true # continue even if this fails for some reason.
+    done
+fi

makefile

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+SRCDIR = $(dir $(realpath $(firstword $(MAKEFILE_LIST))))
+PREFIX ?= /usr
+DESTDIR ?= $(PREFIX)/bin
+
+install:
+	cp -a $(SRCDIR)/lmr.sh $(DESTDIR)/lmr
+
+uninstall:
+	rm $(DESTDIR)/lmr

sloc.sh

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+#!/bin/sh
+
+# SLOC is here defined as lines which are not comments or empty.
+
+# find all *.sh files not under `pkg` that are not symbolic links, strip all
+# trailing whitespace, then all leading whitespace, then all lines starting
+# with '#', then all empty lines. then count the remaining lines.
+
+find . -name "*.sh" ! -path "**/pkg/**" ! -type l \
+| xargs sed 's/[[:space:]]*$//g; s/^[[:space:]]*//g; s/^#.*$//g; /^$/d' \
+| wc -l - \
+| cut -d' ' -f1
+
+# note that this script's SLOC is also included in the count.