quilt/backup-files-restore-symbolic-links.patch

From: Jean Delvare <jdelvare@suse.de>
Date: Wed, 9 Dec 2020 11:39:56 +0100
Subject: backup-files: Restore symbolic links
Patch-mainline: yes
Git-commit: 26f7bc93d2bbe49a96d23f879b24e82651392497
References: https://savannah.nongnu.org/bugs/index.php?59479

As "patch" originally did not handle symbolic links, backup-files
didn't have to care about them either. But now that git has
introduced an extended syntax which allows manipulating symbolic
links in patch files, "quilt push" may create or delete symbolic
links, which means that backup-files must support such operations
too.

Also extend the backup-files test case to cover these operations.

This fixes bug #59479:
https://savannah.nongnu.org/bugs/index.php?59479

Signed-off-by: Jean Delvare <jdelvare@suse.de>
---
 quilt/scripts/backup-files.in |   40 ++++++++++++++++++++++++++++++----------
 test/backup-files.test        |   33 +++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 10 deletions(-)

--- a/quilt/scripts/backup-files.in
+++ b/quilt/scripts/backup-files.in
@@ -89,7 +89,7 @@ backup()
 	dir=$(dirname "$backup")
 	[ -d "$dir" ] || mkdir -p "$dir"
 
-	if [ -e "$file" ]; then
+	if [ -L "$file" -o -e "$file" ]; then
 		$ECHO "Copying $file"
 		if [ -n "$OPT_NOLINKS" -a "$(stat @STAT_HARDLINK@ "$file")" = 1 ]; then
 			cp -p "$file" "$backup"
@@ -110,24 +110,28 @@ restore()
 	local file=$1
 	local backup=$OPT_PREFIX$file
 
-	if [ ! -e "$backup" ]; then
+	if [ ! -L "$backup" -a ! -e "$backup" ]; then
 		return 1
 	fi
-	if [ -s "$backup" ]; then
+	if [ -L "$backup" -o -s "$backup" ]; then
 		$ECHO "Restoring $file"
-		if [ -e "$file" ]; then
+		if [ -L "$file" -o -e "$file" ]; then
 			rm "$file"
 		else
 			mkdir -p "$(dirname "$file")"
 		fi
-		ln "$backup" "$file" 2>&4 || cp -p "$backup" "$file"
+		if [ -L "$backup" ]; then
+			ln -s "$(readlink "$backup")" "$file"
+		else
+			ln "$backup" "$file" 2>&4 || cp -p "$backup" "$file"
+		fi
 
-		if [ -n "$OPT_TOUCH" ]; then
+		if [ -n "$OPT_TOUCH" -a ! -L "$file" ]; then
 			touch "$file"
 		fi
 	else
 		$ECHO "Removing $file"
-		if [ -e "$file" ]; then
+		if [ -L "$file" -o -e "$file" ]; then
 			rm "$file"
 		fi
 	fi
@@ -145,11 +149,13 @@ restore_all()
 	# Store the list of files to process
 	EMPTY_FILES=$(gen_tempfile)
 	NONEMPTY_FILES=$(gen_tempfile)
-	trap "rm -f \"$EMPTY_FILES\" \"$NONEMPTY_FILES\"" EXIT
+	LINK_FILES=$(gen_tempfile)
+	trap "rm -f \"$EMPTY_FILES\" \"$NONEMPTY_FILES\" \"$LINK_FILES\"" EXIT
 
 	cd "$OPT_PREFIX"
 	find . -type f -size 0 -print0 > "$EMPTY_FILES"
 	find . -type f -size +0 -print0 > "$NONEMPTY_FILES"
+	find . -type l -print0 > "$LINK_FILES"
 	cd "$OLDPWD"
 
 	if [ -s "$EMPTY_FILES" ]; then
@@ -189,6 +195,20 @@ restore_all()
 		fi
 	fi
 
+	if [ -s "$LINK_FILES" ]; then
+		(cd "$OPT_PREFIX" && find . -type d -print0) \
+		| xargs -0 mkdir -p
+
+		while read -d $'\0' -r
+		do
+			local file=${REPLY#./}
+			local backup=$OPT_PREFIX$file
+
+			$ECHO "Restoring $file"
+			ln -sf "$(readlink "$backup")" "$file"
+		done < "$LINK_FILES"
+	fi
+
 	if [ -z "$OPT_KEEP_BACKUP" ]; then
 		rm -rf "$OPT_PREFIX"
 	fi
@@ -212,7 +232,7 @@ copy()
 	dir=$(dirname "$backup")
 	[ -d "$dir" ] || mkdir -p "$dir"
 
-	if [ -e "$file" ]; then
+	if [ -L "$file" -o -e "$file" ]; then
 		$ECHO "Copying $file"
 		cp -p "$file" "$backup"
 	else
@@ -234,7 +254,7 @@ copy_many()
 	cat "$OPT_FILE" \
 	| while read
 	do
-		if [ -e "$REPLY" ]; then
+		if [ -L "$REPLY" -o -e "$REPLY" ]; then
 			printf '%s\0' "$REPLY" >&3
 		else
 			# This is a rare case, not worth optimizing
--- a/test/backup-files.test
+++ b/test/backup-files.test
@@ -229,3 +229,36 @@ Unit test of the backup-files script.
 	> 1
 	$ [ ! -s new ] || echo "file snapshot/new should be empty"
 	$ rm -rf snapshot
+
+	# Test backup and restoration of a symbolic link
+	$ mkdir dir
+	$ ln -s foo dir/link
+	$ readlink dir/link
+	> foo
+	$ %{QUILT_DIR}/scripts/backup-files -B backup/ -b dir/link
+	> Copying dir/link
+	$ readlink backup/dir/link
+	> foo
+	$ rm -f dir/link
+	$ echo crap > dir/link
+	$ %{QUILT_DIR}/scripts/backup-files -B backup/ -r -k dir/link
+	> Restoring dir/link
+	$ readlink dir/link
+	> foo
+
+	# Same but reading from a file
+	$ rm -f dir/link
+	$ echo crap > dir/link
+	$ %{QUILT_DIR}/scripts/backup-files -B backup/ -r -k -f -
+	< dir/link
+	> Restoring dir/link
+	$ readlink dir/link
+	> foo
+
+	# Same but without specifying the file
+	$ rm -f dir/link
+	$ echo crap > dir/link
+	$ %{QUILT_DIR}/scripts/backup-files -B backup/ -r -
+	> Restoring dir/link
+	$ readlink dir/link
+	> foo