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

[Laszlo Ersek]

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/$GUEST.log", whenever a guest is started.
>>
>> The information we include in "pkgversion" is the output of git-describe,
>> with a plus sign (+) appended if there are staged or unstaged changes to
>> tracked files, at the time of "configure" being executed.
>>
>> The content of "pkgversion" is not changed when "--with-pkgversion" is
>> used on the command line.
>>
>> Cc: "Daniel P. Berrange" <address@hidden>
>> Cc: Kashyap Chamarthy <address@hidden>
>> Signed-off-by: Laszlo Ersek <address@hidden>
>> ---
>>  configure | 38 ++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 38 insertions(+)
>>
>> diff --git a/configure b/configure
>> index b5aab7257b33..20a7ec5cc0fd 100755
>> --- a/configure
>> +++ b/configure
>> @@ -4255,6 +4255,44 @@ if have_backend "dtrace"; then
>>  fi
>>  
>>  ##########################################
>> +# save git working tree information in pkgversion
>> +
>> +# If pkgversion has not been set to a non-empty string, fetch the output of
>> +# "git describe" into it. If the working tree is unclean (there are staged 
>> or
>> +# unstaged changes in tracked files), then append a plus sign.
>> +#
>> +# If we're not building from a git working tree, then pkgversion is not
>> +# changed. Otherwise, git errors are fatal.
>> +
>> +if test -z "$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?

For example, Debian oldstable ("wheezy"), which I tend to use as one
reference point for "ancient but still supported", has 1.7.10.4:

https://packages.debian.org/wheezy/git

Another example: the latest git package in EPEL-5 is 1.8.2.3:

http://koji.fedoraproject.org/koji/buildinfo?buildID=757915

Thanks
Laszlo