Make qemu-img/qemu-nbd/qemu-io CLI more flexible

This series of patches expands the syntax of the qemu-img, qemu-nbd and qemu-io commands to make them more flexible.

v0: https://lists.gnu.org/archive/html/qemu-devel/2015-10/msg04365.html
v1: https://lists.gnu.org/archive/html/qemu-devel/2015-12/msg04014.html
v2: https://lists.gnu.org/archive/html/qemu-devel/2015-12/msg04354.html
v3: https://lists.gnu.org/archive/html/qemu-devel/2016-01/msg03381.html
v4: https://lists.gnu.org/archive/html/qemu-devel/2016-01/msg04984.html
v5: https://lists.gnu.org/archive/html/qemu-block/2016-02/msg00022.html
v6: https://lists.gnu.org/archive/html/qemu-devel/2016-02/msg03141.html

First all three gain a --object parameter, which allows instantiation of user creatable object types. The immediate use case is to allow for creation of the 'secret' object type to pass passwords for curl, iscsi and rbd drivers. For qemu-nbd this will also be needed to create TLS certificates for encryption support.

Then all three gain a '--image-opts' parameter which causes the positional filenames to be interepreted as option strings rather tha nplain filenames. This avoids the need to use the JSON syntax, or to add custom CLI args for each block backend option that exists. The immediate use case is to allow the user to specify the ID of the 'secret' object they just created.

Finally, there are a few small cleanup patches

NB, this series will conflict with my series adding TLS support to NBD. After one of the series wins the race to merge, I will rebase the other series. I don't mind which merges first really, but the sooner the better considering the forthcoming soft-freeze and that this is a dep for several other patch series.

Changed in v7:

- Rebase to resolve conflicts vs recent NBD patches

Changed in v6:

- Add missing docs of --image-opts for qemu-nbd man page (Eric)
- Remove left over special casing of 'file' in QemuOpts (Kevin)
- Pass NULL to getopt_long when optionindex is not needed (Eric)
- Misc typos in qemu-img docs (Eric)
- Fix qemu-io logic error checking argv/argc opt bounds (Eric)
- Ensure 'id' is passed into blk_open in qemu-img (Kevin)
- Share code for doing block dev passwd prompting

Changed in v5:

- Move more common object creation code into qom/ (Kevin)
- Add missing @var{} syntax in CLI help definition (Kevin)
- Declare QemuOpts closer to time of use (Kevin)
- Directly reference registered opts instead of calling qemu_find_opts (Kevin)
- Use consistent exit/return/goto pattern in qemu-img (Kevin)
- Remove special casing of 'file' in QemuOpts handling for bdrv_open (Kevin)
- Split file file opening code out into separate method (Kevin)

Changed in v4:

- Fix error reporting when object_create fails

Changed in v3:

- Rebase to resolve with conflicts against recently merged code
- Remove use of errx()

Changed in v2:

- Share more common code in qom/object_interfaces.c to avoid duplicating so much of 'object_create' in each command
- Remove previously added '--source optstring' parameter which replaced the positional filenames, in favour of keeping the positional filenames but using a --image-opts boolean arg to change their interpretation
- Added docs for --image-opts to qemu-img man page
- Use printf instead of echo -n in examples
- Line wrap help string based on user terminal width not source code width
- Update qemu-nbd/qemu-io to use constants for options
- Update qemu-nbd to avoid overlapping option values

Daniel P. Berrange (8):
qemu-io: add support for --object command line arg
qemu-img: add support for --object command line arg
qemu-io: allow specifying image as a set of options args
qemu-nbd: allow specifying image as a set of options args
qemu-img: allow specifying image as a set of options args
qemu-nbd: don't overlap long option values with short options
qemu-nbd: use no_argument/required_argument constants
qemu-io: use no_argument/required_argument constants

 qemu-img-cmds.hx |  44 +++---
 qemu-img.c       | 465 +++++++++++++++++++++++++++++++++++++++++++++++++------
 qemu-img.texi    |  14 ++
 qemu-io.c        | 115 +++++++++++---
 qemu-nbd.c       | 104 ++++++++-----
 qemu-nbd.texi    |   7 +-
 6 files changed, 627 insertions(+), 122 deletions(-)

2.5.0