Re: [Qemu-devel] [PATCH] configure: save git working tree information in "pkgversion"

["Daniel P. Berrange" <berrange@redhat.com>]

On Tue, May 31, 2016 at 05:40:38PM +0200, Laszlo Ersek wrote:
> On 05/31/16 17:14, Daniel P. Berrange wrote:
> > On Tue, May 31, 2016 at 05:04:04PM +0200, Laszlo Ersek wrote:
> >> When building QEMU from a git working tree (either in-tree or
> >> out-of-tree), it is useful to capture the working tree status in the QEMU
> >> binary, for the "-version" option to report.
> >>
> >> Daniel suggested using the "pkgversion" variable (tied to the
> >> "--with-pkgversion" option) of the configure script for this. Downstream
> >> packagers of QEMU already use this option for customizing their builds,
> >> plus libvirtd captures "pkgversion" (with the "-version" option) in
> >> "/var/log/libvirt/qemu/$GUEST.log", whenever a guest is started.
> >>
> >> The information we include in "pkgversion" is the output of git-describe,
> >> with a plus sign (+) appended if there are staged or unstaged changes to
> >> tracked files, at the time of "configure" being executed.
> >>
> >> The content of "pkgversion" is not changed when "--with-pkgversion" is
> >> used on the command line.
> >>
> >> Cc: "Daniel P. Berrange" <berrange@redhat.com>
> >> Cc: Kashyap Chamarthy <kchamart@redhat.com>
> >> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> >> ---
> >>  configure | 38 ++++++++++++++++++++++++++++++++++++++
> >>  1 file changed, 38 insertions(+)
> >>
> >> diff --git a/configure b/configure
> >> index b5aab7257b33..20a7ec5cc0fd 100755
> >> --- a/configure
> >> +++ b/configure
> >> @@ -4255,6 +4255,44 @@ if have_backend "dtrace"; then
> >>  fi
> >>  
> >>  ##########################################
> >> +# save git working tree information in pkgversion
> >> +
> >> +# If pkgversion has not been set to a non-empty string, fetch the output of
> >> +# "git describe" into it. If the working tree is unclean (there are staged or
> >> +# unstaged changes in tracked files), then append a plus sign.
> >> +#
> >> +# If we're not building from a git working tree, then pkgversion is not
> >> +# changed. Otherwise, git errors are fatal.
> >> +
> >> +if test -z "$pkgversion" && test -d "$source_path/.git"; then
> >> +  pkgversion=$(
> >> +    export GIT_DIR=$source_path/.git
> >> +    export GIT_WORK_TREE=$source_path
> >> +
> >> +    git_desc=$(git describe)
> >> +    git_exit=$?
> >> +    if test $git_exit -ne 0; then
> >> +      exit $git_exit
> >> +    fi
> >> +
> >> +    git_changes=
> >> +    for git_diff_option in "" --staged; do
> >> +      git diff $git_diff_option --quiet
> >> +      git_exit=$?
> >> +      case $git_exit in
> >> +      (0) ;;
> >> +      (1) git_changes=+
> >> +          ;;
> >> +      (*) exit $git_exit
> >> +          ;;
> >> +      esac
> >> +    done
> > 
> > An alternative to this would be to jus use
> > 
> >  "git describe --dirty"
> > 
> > which appends "--dirty" to its output if working tre has uncommitted
> > changes.
> 
> Good idea!
> 
> > Not sure if the --dirty flag is a recent option or whether we can just
> > assume it always exists.
> 
> Grepping git's Documentation/RelNotes/ directory, I find:
> - in "1.6.6.txt": the introduction of --dirty
> - in "1.7.6.4.txt": an apparently important bugfix for --dirty
> 
> Version 1.7.6.4 of git was tagged on Sep 23 2011.
> 
> Does this information help in deciding if we can use --dirty?

5 years old sounds new enough for my liking :-)

I guess we could use --dirty and catch the non-zero exit code and just
re-try without --dirty.

Regards,
Daniel
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