[mythtv] Github tarball from commit can change

[Alec Leamas]

Ah, and circling back:

On 28/09/15 14:34, Stuart Auchterlonie wrote:
> On 28/09/15 13:17, Craig Treleaven wrote:
>> For my MacPorts packaging of Myth, I use the GitHub feature to create a tarball of the source as of a particular commit.  Work great…most of the time.  But not all the time and not as of yesterday.
>>
>> For example, I updated Myth on September 17 to pull from the fixes-27 branch as of September 9 (commit e9b577d3) and recorded the checksums for the archive at that time.  Yesterday, a user went to build and got different checksums which, of course, caused the build to fail.
>>
>> Comparing the contents of the archive from September 17 to now, the only difference is:
>>
>> $ diff -ur prev new
>> diff -ur prev/MythTV-mythtv-e9b577d/mythtv/EXPORTED_VERSION new/MythTV-mythtv-e9b577d/mythtv/EXPORTED_VERSION
>> --- prev/MythTV-mythtv-e9b577d/mythtv/EXPORTED_VERSION	2015-09-09 13:14:00.000000000 -0400
>> +++ new/MythTV-mythtv-e9b577d/mythtv/EXPORTED_VERSION	2015-09-09 13:14:00.000000000 -0400
>> @@ -1,2 +1,2 @@
>>   SOURCE_VERSION="e9b577d"
>> -BRANCH=" (fixes/0.27)"
>> +BRANCH=“”

 From the git-attribues manpage:

> export-subst
>
> If the attribute export-subst is set for a file then Git will expand several placeholders when adding this file to an archive. The expansion depends on the availability of a commit ID, i.e., if git-archive[1] has been given a tree instead of a commit or a tag then no replacement will be done.

So, the only reason I can think of is that in one case the tarball was 
created from a branch, and in another from an explicit commit. Altough 
they *do* refer to the same set of files, there are subtle differences 
in how git-archive handles the two cases.

--alec