Ar: Update MIME type and add magic numbers

Changes:
  Replace application/x-ar with application/x-archive
  ar magic number:  "!<arch>\n"
  deb magic number (Debian 0.93+): "!<arch>\ndebian-binary"

REF:
  https://en.wikipedia.org/wiki/Ar_(Unix)
  https://en.wikipedia.org/wiki/Deb_(file_format)

Test:
  $ touch a && touch b && ar r test.ar a b && cp test.ar test-2.a

  $ xdg-mime query filetype test.ar
  application/x-archive

  $ xdg-mime query filetype dftp_2.2-1.deb
  application/vnd.debian.binary-package

  $ gio info test.ar | grep content-type
  standard::content-type: application/x-archive
  standard::fast-content-type: application/x-archive

  $ gio info dftp_2.2-1.deb | grep content-type
  standard::content-type: application/vnd.debian.binary-package
  standard::fast-content-type: application/vnd.debian.binary-package

  $ hexdump -C -n 8 test.ar
  00000000  21 3c 61 72 63 68 3e 0a                           |!<arch>.|
  00000008

  $ hexdump -C -n 21 dftp_2.2-1.deb
  00000000  21 3c 61 72 63 68 3e 0a  64 65 62 69 61 6e 2d 62  |!<arch>.debian-b|
  00000010  69 6e 61 72 79                                    |inary|
  00000015

  $ ./autogen.sh --prefix=/usr --disable-magic && make && sudo make install

5 files changed, 12 insertions, 10 deletions

diff --git a/caja/caja-engrampa.c b/caja/caja-engrampa.c
index 8e1a8f2..3667b5a 100644
--- a/caja/caja-engrampa.c
+++ b/caja/caja-engrampa.c
@@ -149,7 +149,7 @@ static struct {
 		{ "application/x-7z-compressed-tar", TRUE },
 		{ "application/x-ace", TRUE },
 		{ "application/x-alz", TRUE },
-		{ "application/x-ar", TRUE },
+		{ "application/x-archive", TRUE },
 		{ "application/x-arj", TRUE },
 		{ "application/x-brotli", TRUE },
 		{ "application/x-brotli-compressed-tar", TRUE },
diff --git a/data/engrampa.desktop.in.in b/data/engrampa.desktop.in.in
index 26ccf0c..7222ba6 100644
--- a/data/engrampa.desktop.in.in
+++ b/data/engrampa.desktop.in.in
@@ -9,7 +9,7 @@ Terminal=false
 Type=Application
 Icon=engrampa
 Categories=GTK;Utility;Archiving;Compression;
-MimeType=application/x-7z-compressed;application/x-7z-compressed-tar;application/x-ace;application/x-alz;application/x-ar;application/x-arj;application/x-brotli;application/x-brotli-compressed-tar;application/x-bzip;application/x-bzip-compressed-tar;application/x-bzip1;application/x-bzip1-compressed-tar;application/x-cabinet;application/x-cbr;application/x-cbz;application/x-cd-image;application/x-compress;application/x-compressed-tar;application/x-cpio;application/vnd.debian.binary-package;application/x-ear;application/x-ms-dos-executable;application/x-gtar;application/x-gzip;application/x-gzpostscript;application/x-java-archive;application/x-lha;application/x-lzh-compressed;application/x-lrzip;application/x-lrzip-compressed-tar;application/x-lzip;application/x-lzip-compressed-tar;application/x-lzma;application/x-lzma-compressed-tar;application/x-lzop;application/x-lzop-compressed-tar;application/x-ms-wim;application/x-rar;application/x-rar-compressed;application/x-rpm;application/x-rzip;application/x-tar;application/x-tarz;application/x-stuffit;application/x-war;application/x-xz;application/x-xz-compressed-tar;application/x-zip;application/x-zip-compressed;application/x-zoo;application/zip;application/x-archive;application/vnd.ms-cab-compressed;application/zstd;
+MimeType=application/x-7z-compressed;application/x-7z-compressed-tar;application/x-ace;application/x-alz;application/x-arj;application/x-brotli;application/x-brotli-compressed-tar;application/x-bzip;application/x-bzip-compressed-tar;application/x-bzip1;application/x-bzip1-compressed-tar;application/x-cabinet;application/x-cbr;application/x-cbz;application/x-cd-image;application/x-compress;application/x-compressed-tar;application/x-cpio;application/vnd.debian.binary-package;application/x-ear;application/x-ms-dos-executable;application/x-gtar;application/x-gzip;application/x-gzpostscript;application/x-java-archive;application/x-lha;application/x-lzh-compressed;application/x-lrzip;application/x-lrzip-compressed-tar;application/x-lzip;application/x-lzip-compressed-tar;application/x-lzma;application/x-lzma-compressed-tar;application/x-lzop;application/x-lzop-compressed-tar;application/x-ms-wim;application/x-rar;application/x-rar-compressed;application/x-rpm;application/x-rzip;application/x-tar;application/x-tarz;application/x-stuffit;application/x-war;application/x-xz;application/x-xz-compressed-tar;application/x-zip;application/x-zip-compressed;application/x-zoo;application/zip;application/x-archive;application/vnd.ms-cab-compressed;application/zstd;
 Keywords=MATE;archive;manager;compression;
 X-MATE-DocPath=engrampa/engrampa.xml
 X-MATE-Bugzilla-Bugzilla=MATE
diff --git a/src/fr-archive.c b/src/fr-archive.c
index c41aa7e..eff0afe 100644
--- a/src/fr-archive.c
+++ b/src/fr-archive.c
@@ -550,6 +550,8 @@ get_mime_type_from_magic_numbers (GFile *file)
 		const char * const mime_type;
 	} magic_ids [] = {
 		/* magic ids taken from magic/Magdir/archive from the file-4.21 tarball */
+		{ 0, 21, "!<arch>" "\x0a" "debian-binary",       "application/vnd.debian.binary-package" },
+		{ 0,  8, "!<arch>" "\x0a",                       "application/x-archive"       },
 		{ 0,  6, "7z\274\257\047\034",                   "application/x-7z-compressed" },
 		{ 7,  7, "**ACE**",                              "application/x-ace"           },
 		{ 0,  2, "\x60\xea",                             "application/x-arj"           },
diff --git a/src/fr-command-ar.c b/src/fr-command-ar.c
index 12eee41..f72444a 100644
--- a/src/fr-command-ar.c
+++ b/src/fr-command-ar.c
@@ -241,9 +241,9 @@ fr_command_ar_handle_error (FrCommand   *comm,
 }
 
 
-const char *ar_mime_type[] = { "application/x-ar",
-			       "application/vnd.debian.binary-package",
-			       NULL };
+const char *ar_mime_type[] = { "application/x-archive",
+                               "application/vnd.debian.binary-package",
+                               NULL };
 
 
 static const char **
@@ -264,7 +264,7 @@ fr_command_ar_get_capabilities (FrCommand  *comm,
 	if (is_program_available ("ar", check_command)) {
 		if (is_mime_type (mime_type, "application/vnd.debian.binary-package"))
 			capabilities |= FR_COMMAND_CAN_READ;
-		else if (is_mime_type (mime_type, "application/x-ar"))
+		else if (is_mime_type (mime_type, "application/x-archive"))
 			capabilities |= FR_COMMAND_CAN_READ_WRITE;
 	}
 
diff --git a/src/fr-init.c b/src/fr-init.c
index 8c06372..33bdf53 100644
--- a/src/fr-init.c
+++ b/src/fr-init.c
@@ -71,8 +71,8 @@ FrMimeTypeDescription mime_type_desc[] = {
 	{ "application/x-7z-compressed-tar",                          ".tar.7z",   N_("Tar compressed with 7z (.tar.7z)"), 0 },
 	{ "application/x-ace",                                        ".ace",      N_("Ace (.ace)"), 0 },
 	{ "application/x-alz",                                        ".alz",      N_("ALZip archive (.alz)"), 0 },
-	{ "application/x-ar",                                         ".a",        N_("Ar (.a)"), 0 },
-	{ "application/x-ar",                                         ".ar",       N_("Ar (.ar)"), 0 },
+	{ "application/x-archive",                                    ".a",        N_("Ar (.a)"), 0 },
+	{ "application/x-archive",                                    ".ar",       N_("Ar (.ar)"), 0 },
 	{ "application/x-arj",                                        ".arj",      N_("Arj (.arj)"), 0 },
 	{ "application/x-brotli",                                     ".br",       N_("brotli (.br)"), 0 },
 	{ "application/x-brotli-compressed-tar",                      ".tar.br",   N_("Tar compressed with brotli (.tar.br)"), 0 },
@@ -117,10 +117,10 @@ FrMimeTypeDescription mime_type_desc[] = {
 
 FrExtensionType file_ext_type[] = {
 	{ ".7z", "application/x-7z-compressed" },
-	{ ".a", "application/x-ar" },
+	{ ".a", "application/x-archive" },
 	{ ".ace", "application/x-ace" },
 	{ ".alz", "application/x-alz" },
-	{ ".ar", "application/x-ar" },
+	{ ".ar", "application/x-archive" },
 	{ ".arj", "application/x-arj" },
 	{ ".bin", "application/x-stuffit" },
 	{ ".br", "application/x-brotli" },