dgit: quilt fixup: Don't use dpkg-source --commit, but git diff

There are many things that dpkg-source can successfully extract, but
which it can't create.  (This is because dpkg-source largely delegates
application to diff(1), and diff can do many more things nowadays.)

Most real packages were made with git-format-patch or equivalent
nowadays, so use of these features is common.  (Hence #949675
and #995056, where even glibc has patches that dpkg-source cannot make.)

Right now the practical consequences are:

 * Creating an executable file is fixed.  This actually completes
   the work for #949675.

 * Creating a symlink has a regression in the error handling.
   Previously, dpkg-source --commit failed during quilt fixup.
   Now, we happily git diff which generates a patch that dpkg-source
   can't apply.  We're going to fix this soon by aligning the
   representable change checking with reality.

 * It's faster and less complicated.

Closes: #1018143
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/tests/unrepresentable b/tests/tests/unrepresentable
index c9ba11c..fa1f985 100755
--- a/tests/tests/unrepresentable
+++ b/tests/tests/unrepresentable
@@ -115,7 +115,7 @@ finish EP:'deletion of symlink' LATE-EP:'Mode change from 20000 to 000000'
 start new
 	ln -s hi new
 	git add new
-finish 'new version is symlink' 'new version is symlink'
+finish BUILD:'modifies file work/new through a symlink' 'new version is symlink'
 
 start src.c
 	git rm src.c
@@ -138,7 +138,7 @@ start newx
 	echo hi >newx
 	chmod 755 newx
 	git add newx
-finish BUILD:'differs .* debian/patches' LATE-EP:'Mode change from 644 to 755'
+finish GOOD:add-755 LATE-EP:'Mode change from 644 to 755'
 
 start nothing
 finish NOTHING NOTHING