Restructure, and rewrite substantial partsHEADmasterdevel

A notable problem (to me) with the former version was, that upon simple
movements in the source file tree, these would in general cause
duplicated data in the backup forest.  This problem has been resolved
by essentially tracking file movements, using hard links.

Also, the code has been divided into several different files, extranous
code removed, the organization of remote code execution simplified.

In the process of simplification, all parts requiring direct interaction
of the user with the program have been replaced.  In most cases, this
means that the program now just terminates with an error instead of
allowing the user to confirm deletion of an unexpected (remnant) file.
This may be considered a drawback, but actually these interactive
options were anyways suboptimal solutions in most cases - where they
occured, which was due to remnant files of aborted or failed former
backups.

In general, there have been a lot of changes.  Which are not thoroughly
documented here.  Since there is often no strong relation to the old
code, this is not deemed necessary, as the in-code documentation is
expected to be of sufficient help.

Also, there has been added a little general documentation in the README
and particularly the NOTES file.

It is to be noted that this new version is far from sophisticated.  It
has been tested with and is in use for real data, however lacks a lot of
convenience.  In particular, if a backup fails unexpectedly, the next
backup will in the very most cases loudly fail without manual
intervention.  Also, the program is not able to continue the growth of a
backup tree built with former versions of this program, by itself.  This
can however be arranged by hand.

1 files changed, 153 insertions, 0 deletions

diff --git a/files b/files
new file mode 100644
index 0000000..85640e7
--- /dev/null
+++ b/files
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+#!/usr/bin/env bash
+#
+# files - functions acting on files.
+#
+# Copyright 2015 - 2019 Einhard Leichtfuß
+#
+# This file is part of rsync-backup.
+#
+# rsync-backup is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published
+# by the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# rsync-backup 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with rsync-backup.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+
+# Create directory, unless it exists already.  Returns non-zero, if the
+# named file exists however is not a directory.
+#
+# $1: directory: path
+#
+function create_dir
+{
+	local dir="$1"
+
+	if [[ ! -e "$dir" && ! -L "$dir" ]]
+	then
+		mkdir "$dir" || return $RET_ERROR
+	elif [[ ! -d "$dir" || -L "$dir" ]]
+	then
+		error "\"$dir\" is not a directory."
+		return $RET_FILE_ERR
+	fi
+
+	return $RET_SUCCESS
+}
+
+
+# Create a new directory, assuring it did not exist before.
+#
+# $1: directory: path
+#
+function create_new_dir
+{
+	local dir="$1"
+
+	if [[ -e "$dir" || -L "$dir" ]]
+	then
+		error "\"$dir\" exists already."
+		return $RET_FILE_ERR
+	fi
+
+	mkdir "$dir" || return $RET_ERROR
+
+	return $RET_SUCCESS
+}
+
+
+# Verify the specified file is a directory.
+#
+# $1: directory: path
+#
+function assert_is_dir
+{
+	local dir="$1"
+
+	if [[ ! -d "$dir" || -L "$dir" ]]
+	then
+		error "\"$dir\" is not a directory."
+		return $RET_FILE_ERR
+	fi
+
+	return $RET_SUCCESS
+}
+
+
+# Replace symbolic link $2 by symbolic link $1.  $2 may not exist.
+#
+# $1: source file name: path
+# $2: target file name: path
+#
+function replace_symlink
+{
+	local src="$1"
+	local tgt="$2"
+
+	if [[ ! -L "$src" ]]
+	then
+		error "\"$src\" is not a symbolic link."
+		return $RET_FILE_ERR
+	fi
+
+	if [[ ! -L "$tgt" && -e "$tgt" ]]
+	then
+		error "\"$tgt\" is not a symbolic link."
+		return $RET_FILE_ERR
+	fi
+
+	mv -T "$src" "$tgt" || return $RET_ERROR
+
+	return $RET_SUCCESS
+}
+
+
+# Replace symbolic link $1's target by $2.  $1 may not exist.
+#
+# $1: link file: path
+# $2: link target: path
+#
+function replace_symlink_target
+{
+	local link="$1"
+	local tgt="$2"
+
+	if [[ ! -L "$link" && -e "$link" ]]
+	then
+		error "\"$link\" is not a symbolic link."
+		return $RET_FILE_ERR
+	fi
+
+	ln -sfT "$tgt" "$link" || return $RET_ERROR
+
+	return $RET_SUCCESS
+}
+
+
+# Remove a symbolic link.
+#
+# $1: link: path
+#
+function remove_symlink
+{
+	local file="$1"
+
+	if [[ ! -L "$file" ]]
+	then
+		error "\"$file\" is not a symbolic link."
+		return $RET_FILE_ERR
+	fi
+
+	rm "$file" || return $RET_ERROR
+
+	return $RET_SUCCESS
+}
+
+# vi: ft=bash ts=2 sw=2 noet