[PATCH v2] Use GBP_EXPORT_ORIG_OPTIONS for dpg-gbp export command

[Uladzimir Bely <ubely@ilbers.de>]

Since we now use `gbp export-orig <options>` and they need different
options than `gbp buildpackage`, we should store these options in
different variable.

This patch intruduces `GBP_EXPORT_ORIG_OPTIONS` variable and
describes it in RECIPE-API-CHANGELOG.

Signed-off-by: Uladzimir Bely <ubely@ilbers.de>
---
 RECIPE-API-CHANGELOG.md       | 16 ++++++++++++++++
 meta/classes/dpkg-gbp.bbclass |  4 ++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/RECIPE-API-CHANGELOG.md b/RECIPE-API-CHANGELOG.md
index 0bb83389..8013e585 100644
--- a/RECIPE-API-CHANGELOG.md
+++ b/RECIPE-API-CHANGELOG.md
@@ -441,3 +441,19 @@ exist, empty variables are forwarded.
 
 **Note about reproducibility**: the forwarded variables must not have any influence on the generated package.
 This mechanism must also not be used to inject build configurations. For these cases, templates should be used.
+
+### Switch to `gbp export-orig` and `GBP_EXPORT_ORIG_OPTIONS`
+
+Since Debian Stretch support is removed, we can now use short `gbp export-orig`
+instead of long `gbp buildpackage --git-ignore-new --git-builder=/bin/true`
+to prepare gbp-based sources for building.
+
+Options for `export-orig` should be specified with `GBP_EXPORT_ORIG_OPTIONS`
+variable in favor of previously used `GBP_EXTRA_OPTIONS` one. For example:
+
+```
+GBP_EXTRA_OPTIONS = "--git-no-pristine-tar --git-upstream-branch=master"
+GBP_EXPORT_ORIG_OPTIONS = "--no-pristine-tar --upstream-branch=master"
+```
+
+To support both old and new Isar, custom recipe should have both variables.
diff --git a/meta/classes/dpkg-gbp.bbclass b/meta/classes/dpkg-gbp.bbclass
index f765eb9a..4e29f62d 100644
--- a/meta/classes/dpkg-gbp.bbclass
+++ b/meta/classes/dpkg-gbp.bbclass
@@ -9,13 +9,13 @@ S = "${WORKDIR}/git"
 
 PATCHTOOL ?= "git"
 
-GBP_EXTRA_OPTIONS ?= "--pristine-tar"
+GBP_EXPORT_ORIG_OPTIONS ?= "--pristine-tar"
 
 SCHROOT_MOUNTS = "${WORKDIR}:${PP} ${GITDIR}:/home/.git-downloads"
 
 dpkg_runbuild_prepend() {
     sh -c "
         cd ${WORKDIR}/${PPS}
-        gbp export-orig ${GBP_EXTRA_OPTIONS}
+        gbp export-orig ${GBP_EXPORT_ORIG_OPTIONS}
     "
 }
-- 
2.20.1

Changes since v1:
- Fixed typo in commit message