[PATCH] meta/image: allow customization of command we use fo BUILD_ID

[Henning Schild <henning.schild@siemens.com>]

One of the previous patches introduced the feature to leave some build
system information in the rootfs. The git command to derive that
information was kept pretty repository agnostic.

This patch makes the command Isar-specific and allows users to customize
the command to their needs if they use a different tagging scheme in
their repository, or if they do not use git at all.

Signed-off-by: Henning Schild <henning.schild@siemens.com>
---
 meta-isar/recipes-core/images/isar-image-base.bb |  3 ++-
 meta/classes/image.bbclass                       | 27 ++++++++++++------------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/meta-isar/recipes-core/images/isar-image-base.bb b/meta-isar/recipes-core/images/isar-image-base.bb
index c72bfdb..a24aa3e 100644
--- a/meta-isar/recipes-core/images/isar-image-base.bb
+++ b/meta-isar/recipes-core/images/isar-image-base.bb
@@ -24,7 +24,8 @@ IMAGE_TRANSIENT_PACKAGES += "isar-cfg-localepurge"
 
 WORKDIR = "${TMPDIR}/work/${DISTRO}-${DISTRO_ARCH}/${PN}"
 
-ISAR_GIT_RELEASE_PATH ?= "${LAYERDIR_isar}"
+ISAR_RELEASE_CMD_DEFAULT = "git -C ${LAYERDIR_isar} describe --tags --dirty --match 'v[0-9].[0-9]*'"
+ISAR_RELEASE_CMD ?= "${ISAR_RELEASE_CMD_DEFAULT}"
 
 do_rootfs[root_cleandirs] = "${IMAGE_ROOTFS} \
                              ${IMAGE_ROOTFS}/isar-apt"
diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index 7935b69..077c550 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -34,24 +34,25 @@ def get_rootfs_size(d):
 
     return base_size + rootfs_extra * 1024
 
-# we assume that one git commit can describe the whole image, so you should be
-# using submodules, kas, or something like that
-# set ISAR_GIT_RELEASE_PATH to that one "most significant" layer
-# when not using git, override do_mark_rootfs
+# here we call a command that should describe your whole build system,
+# this could be "git describe" or something similar.
+# set ISAR_RELEASE_CMD to customize, or override do_mark_rootfs to do something
+# completely different
 def get_build_id(d):
     import subprocess
     if (len(d.getVar("BBLAYERS", True).strip().split(' ')) != 2 and
-        (d.getVar("ISAR_GIT_RELEASE_PATH", True) ==
-         d.getVar("LAYERDIR_isar", True))):
+        (d.getVar("ISAR_RELEASE_CMD", True) ==
+         d.getVar("ISAR_RELEASE_CMD_DEFAULT", True))):
         bb.warn('You are using external layers that will not be considered' +
-                ' in the build_id. Considder setting ISAR_GIT_RELEASE_PATH.')
-    base = ["git", "-C", d.getVar("ISAR_GIT_RELEASE_PATH", True)]
-    if (0 == subprocess.call(base + ["rev-parse"])):
-        v = subprocess.check_output(base +
-                                    ["describe", "--long", "--dirty",
-                                     "--always"], universal_newlines=True)
+                ' in the build_id. Consider changing ISAR_RELEASE_CMD.')
+    cmd = d.getVar("ISAR_RELEASE_CMD", True)
+    try:
+        v = subprocess.check_output(cmd, shell=True, universal_newlines=True)
         return v.rstrip()
-    return ""
+    except subprocess.CalledProcessError as e:
+        bb.warn('\"%s\" returned %d, returning empty build_id' %
+                (e.cmd, e.returncode))
+        return ""
 
 python set_image_size () {
     rootfs_size = get_rootfs_size(d)
-- 
2.16.4