Import: Use absurd `git apply' emulation if gbp pq import fails

gbp import can fail due to git apply not understanding patches.
This is #841867 (against dgit).

The underlying problem is #841866 (in gbp pq) which exposes things
like #841865 and #829067 (in git).  I imagine there are other lurking
incompatibilities between git-apply and dpkg-source.

We could in principle reimplement the gbp patch metadata extraction.
But that would be quite tiresome and have its own compatibility
problems.

The real problem is just `git apply'.  (Indeed gbp already tries git
apply without, and then with, a whitespace fix option.)  We work
around the trouble by providing our own implementation of `git apply'.

Specifically:

We try to do things the sane way (just running gbp pq import) first.
If that works, great.  If it doesn't, we put /usr/share/dgit/absurd on
the PATH.  That contains only a sh script called `git'.  This sh
script figures out whether the caller is trying to invoke `git apply'.
If not, it runs the real git.

If the caller wanted git-apply, the absurd git script emulates it
using dpkg-source --before-build.  Conveniently, we know that the
series file will not be touched by patches.  So we can write just the
patch we care about into the series file, and run --before-build,
which applies just that one patch.

The results are committed (minus the .pc), and for the next patch,
dpkg-source sees again a tree with simply a single patch to apply.

We try ordinary gbp pq first because our absurd approach is very slow
on a big tree.  Also we would like to maximise our chances of the
import working.  If git and/or gbp ever work better by themselves, all
of this craziness will simply not happen.

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

diff --git a/Makefile b/Makefile
index b72a1e9f477f61e1c7edcda2afa4e2e9796170a5..9491e4dcdb1364d9483afce5c60585660d3164c8 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -37,6 +37,7 @@ MAN1PAGES=dgit.1
 MAN7PAGES=dgit.7 dgit-maint-merge.7
 TXTDOCS=README.dsc-import
 PERLMODULES=Debian/Dgit.pm
+ABSURDITIES=git
 
 INFRA_PROGRAMS=dgit-repos-server dgit-ssh-dispatch \
        dgit-repos-policy-debian dgit-repos-admin-debian \
@@ -57,6 +58,8 @@ substituted/%:        %
 install:       installdirs all
        $(INSTALL_PROGRAM) $(addprefix substituted/,$(PROGRAMS)) \
                $(DESTDIR)$(bindir)
+       $(INSTALL_PROGRAM) $(addprefix absurd/,$(ABSURDITIES)) \
+               $(DESTDIR)$(absurddir)
        $(INSTALL_DATA) $(MAN1PAGES) $(DESTDIR)$(man1dir)
        $(INSTALL_DATA) $(MAN7PAGES) $(DESTDIR)$(man7dir)
        $(INSTALL_DATA) $(TXTDOCS) $(DESTDIR)$(txtdocdir)

diff --git a/absurd/git b/absurd/git
new file mode 100755 (executable)
index 0000000..039bbf0
--- /dev/null
+++ b/absurd/git
@@ -0,0 +1,70 @@
+#!/bin/sh
+set -e
+
+fail () {
+       echo >&2 "DGIT ABSURD GIT APPLY - FAILED: $*"
+       exit 127
+}
+
+self=${0%/*}
+npath=${PATH#$self:}
+if test "x$PATH" = "x$npath"; then
+       fail "PATH FILTER FAIL ($0 $self $PATH)"
+fi
+
+bypass=true
+for arg in "$@"; do
+       case "$arg" in
+       apply)  bypass=false; break     ;;
+       -*)                             ;;
+       *)      bypass=true; break      ;;
+       esac
+done
+
+if $bypass; then
+       PATH=$npath
+       exec git "$@"
+fi
+
+echo >&2 "DGIT ABSURD GIT APPLY - NO BYPASS: $*"
+
+#exec >/dev/tty 2>&1
+
+index=0
+noo=0
+
+for arg in "$@"; do
+       case "$noo.$arg" in
+       1.--index)
+               index=1
+               continue
+               ;;
+       ?.-*)
+               fail "UNKNOWN OPTION $arg ($*)"
+               ;;
+       0.apply)
+               ;;
+       1.*)    patch="$arg"
+               ;;
+       *)
+               fail "BAD USAGE $arg ($noo $*)"
+       esac
+       noo=$(( $noo + 1 ))
+done
+
+if [ $noo != 2 ]; then
+       fail "NO PATCH ($*)"
+fi
+
+pwd=`pwd`
+patch=${patch#$pwd/debian/patches/}
+printf "%s\n" "$patch" >debian/patches/series
+
+dpkg-source --before-build .
+
+rm -rf .pc
+git checkout debian/patches/series
+git add -Af .
+
+echo >&2 "DGIT ABSURD GIT APPLY - APPLIED $patch"
+#printf 'APPLIED '; date --iso-8601=ns

diff --git a/dgit b/dgit
index 344d006692e40a80b40517d58e83502c16284020..f821299f4d06e129de1be4ba6093fac50c867789 100755 (executable)
--- a/dgit
+++ b/dgit
@@ -1954,25 +1954,48 @@ END
        local $ENV{GIT_AUTHOR_EMAIL} = $authline[1];
        local $ENV{GIT_AUTHOR_DATE} =  $authline[2];
 
-       eval {
-           runcmd shell_cmd 'exec >/dev/null 2>../../gbp-pq-output',
-               gbp_pq, qw(import);
-       };
-       if ($@) {
-           { local $@; eval { runcmd qw(cat ../../gbp-pq-output); }; }
-           die $@;
-       }
+       my $path = $ENV{PATH} or die;
+
+       foreach my $use_absurd (qw(0 1)) {
+           local $ENV{PATH} = $path;
+           if ($use_absurd) {
+               chomp $@;
+               progress "warning: $@";
+               $path = "$absurdity:$path";
+               progress "$us: trying slow absurd-git-apply...";
+               rename "../../gbp-pq-output","../../gbp-pq-output.0"
+                   or die $!;
+           }
+           eval {
+               local $ENV{PATH} = $path if $use_absurd;
+
+               my @showcmd = (gbp_pq, qw(import));
+               my @realcmd = shell_cmd
+                   'exec >/dev/null 2>../../gbp-pq-output', @showcmd;
+               debugcmd "+",@realcmd;
+               if (system @realcmd) {
+                   die +(shellquote @showcmd).
+                       " failed: ".
+                       failedcmd_waitstatus()."\n";
+               }
 
-       my $gapplied = git_rev_parse('HEAD');
-       my $gappliedtree = cmdoutput @git, qw(rev-parse HEAD:);
-       $gappliedtree eq $dappliedtree or
-           fail <<END;
+               my $gapplied = git_rev_parse('HEAD');
+               my $gappliedtree = cmdoutput @git, qw(rev-parse HEAD:);
+               $gappliedtree eq $dappliedtree or
+                   fail <<END;
 gbp-pq import and dpkg-source disagree!
  gbp-pq import gave commit $gapplied
  gbp-pq import gave tree $gappliedtree
  dpkg-source --before-build gave tree $dappliedtree
 END
-       $rawimport_hash = $gapplied;
+               $rawimport_hash = $gapplied;
+           };
+           last unless $@;
+       }
+       if ($@) {
+           { local $@; eval { runcmd qw(cat ../../gbp-pq-output); }; }
+           die $@;
+       }
     }
 
     progress "synthesised git commit from .dsc $cversion";