qemu-img: Add -F shorthand to convert

Although we have long supported 'qemu-img convert -o
backing_file=foo,backing_fmt=bar', the fact that we have a shortcut -B
for backing_file but none for backing_fmt has made it more likely that
users accidentally run into:

qemu-img: warning: Deprecated use of backing file without explicit backing format

when using -B instead of -o.  For similarity with other qemu-img
commands, such as create and compare, add '-F $fmt' as the shorthand
for '-o backing_fmt=$fmt'.  Update iotest 122 for coverage of both
spellings.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210913131735.1948339-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/qemu-img.c b/qemu-img.c
index e43a71a..f036a1d 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2183,7 +2183,8 @@ static int img_convert(int argc, char **argv)
     int c, bs_i, flags, src_flags = BDRV_O_NO_SHARE;
     const char *fmt = NULL, *out_fmt = NULL, *cache = "unsafe",
                *src_cache = BDRV_DEFAULT_CACHE, *out_baseimg = NULL,
-               *out_filename, *out_baseimg_param, *snapshot_name = NULL;
+               *out_filename, *out_baseimg_param, *snapshot_name = NULL,
+               *backing_fmt = NULL;
     BlockDriver *drv = NULL, *proto_drv = NULL;
     BlockDriverInfo bdi;
     BlockDriverState *out_bs;
@@ -2223,7 +2224,7 @@ static int img_convert(int argc, char **argv)
             {"skip-broken-bitmaps", no_argument, 0, OPTION_SKIP_BROKEN},
             {0, 0, 0, 0}
         };
-        c = getopt_long(argc, argv, ":hf:O:B:Cco:l:S:pt:T:qnm:WUr:",
+        c = getopt_long(argc, argv, ":hf:O:B:CcF:o:l:S:pt:T:qnm:WUr:",
                         long_options, NULL);
         if (c == -1) {
             break;
@@ -2253,6 +2254,9 @@ static int img_convert(int argc, char **argv)
         case 'c':
             s.compressed = true;
             break;
+        case 'F':
+            backing_fmt = optarg;
+            break;
         case 'o':
             if (accumulate_options(&options, optarg) < 0) {
                 goto fail_getopt;
@@ -2521,7 +2525,7 @@ static int img_convert(int argc, char **argv)
 
         qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
                             s.total_sectors * BDRV_SECTOR_SIZE, &error_abort);
-        ret = add_old_style_options(out_fmt, opts, out_baseimg, NULL);
+        ret = add_old_style_options(out_fmt, opts, out_baseimg, backing_fmt);
         if (ret < 0) {
             goto out;
         }