[Qemu-block] [PATCH] qemu-img: Improve commit invalid base message

[Max Reitz]

When trying to invoke qemu-img commit with a base image file name that
is not part of the top image's backing chain, the user receives a rather
plain "Base not found" error message. This is not really helpful because
it does not explain what "not found" means, potentially leaving the user
wondering why qemu cannot find a file despite it clearly existing in the
file system.

Improve the error message by clarifying that "not found" means "not
found in the top image's backing chain".

Reported-by: Ala Hino <address@hidden>
Signed-off-by: Max Reitz <address@hidden>
---
Reported in: https://bugzilla.redhat.com/show_bug.cgi?id=1390991
---
 qemu-img.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/qemu-img.c b/qemu-img.c
index 6949b73..d020e9a 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -912,7 +912,9 @@ static int img_commit(int argc, char **argv)
     if (base) {
         base_bs = bdrv_find_backing_image(bs, base);
         if (!base_bs) {
-            error_setg(&local_err, QERR_BASE_NOT_FOUND, base);
+            error_setg(&local_err,
+                       "Did not find '%s' in the backing chain of '%s'",
+                       base, filename);
             goto done;
         }
     } else {
-- 
2.10.2