[Libguestfs] fixes for building guestfs-tools and virt-v2v against a fresh libguestfs

[Laszlo Ersek]

Hi,

I'll post two small patch sets as followups to this "higher order" cover
letter. The goal is to build guestfs-tools and virt-v2v against a
freshly built libguestfs (git checkout), using libguestfs's "run"
script. The modifications affect two projects, libguestfs-common and
guestfs-tools, hence the two (upcoming) patch series.

libguestfs-common is tricky because it is consumed as a submodule by
three git superprojects (libguestfs itself, then guestfs-tools and
virt-v2v). Yet more trickily, the three superprojects don't all seem to
consume libguestfs-common at the same submodule git commit, at the
moment. (libguestfs and guestfs-tools consume the submodule at older
commit 74bc5c5c5cb4, while virt-v2v consumes the submodule at current
HEAD commit 6d26b6eac9da.)

For verifying the libguestfs-common updates, I first attempted various
git-pushes into the submodule checkouts of the superprojects. That
proved super unwieldy, as it would require a whole lot of git massaging
just to (incrementally) rebuild all three superprojects after each
libguestfs-common update. Instead, in each superproject, I created a
development branch, and as first commit on that branch, I removed the
submodule altogether, and replaced it with a directory tree of symbolic
links into my stand-alone libguestfs-common worktree -- refer to the
"lndir" command. I didn't expect creating new files in
libguestfs-common, so once established, the symlink set could be
considered final. Furthermore, "lndir" was required for symlinking
individual regular files: symlinking subdirectories from
libguestfs-common into the superprojects' "common" directories doesn't
work, as the "common" content refers back to the superproject, via
relative pathnames such as "../blah". For such pathnames to work, the
deep "common" directory structure actually needs to exist within each
superproject, only the leaves (the regular files) can be replaced with
symlinks. Thankfully, "lndir" implements just that.

This effectively bumped libguestfs and guestfs-tools to
libguestfs-common HEAD commit 6d26b6eac9da, as a basis for the needed
libguestfs-common fixes.

With the "libguestfs-common" patch set applied (on top of commit
6d26b6eac9da), libguestfs can be built and checked without regressions.
Furthermore, virt-v2v too can be built and checked against the
just-built libguestfs (using the latter's "run" script) without regressions.

The same applies to "guestfs-tools", assuming the other patch set is
applied to it (on top of commit 9ba463545fa0).

Once these patch sets are up-stream, the three superprojects should
advance their submodule references to the new libguestfs-common head commit.

Thanks!
Laszlo