[PATCH 4/5] doc: write something about "debianize"

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

From: Henning Schild <henning.schild@siemens.com>

Also add some comments to the implementation and extend the example
recipe with some pre- and post-processing.

Signed-off-by: Henning Schild <henning.schild@siemens.com>
---
 doc/user_manual.md                            | 19 ++++++++++++++++++-
 .../recipes-app/samefile/samefile_2.14.bb     | 14 ++++++++++++++
 meta/classes/debianize.bbclass                |  6 ++++++
 3 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/doc/user_manual.md b/doc/user_manual.md
index 34f50df..7c23fcc 100644
--- a/doc/user_manual.md
+++ b/doc/user_manual.md
@@ -583,7 +583,7 @@ Isar currently supports two ways of creating custom packages.
 
 The `deb` packages are built using `dpkg-buildpackage`, so the sources should contain the `debian` directory with necessary meta information. This way is the default way of adding software that needs to be compiled from source. The bbclass for this approach is called `dpkg`.
 
-**NOTE:** If the sources do not contain a `debian` directory your recipe can fetch, create, or ship that.
+**NOTE:** If the sources do not contain a `debian` directory your recipe can fetch, create, or ship that. You might want to read the the next section before returning here.
 
 This is also what you do if you want to rebuild/modify an upstream package.
 Isar does understand `SRC_URI` entries starting with "apt://". For an example
@@ -624,6 +624,23 @@ This approach prevents duplication of the license files in different packages.
 
 The last line in the example above adds recipe to the Isar work chain.
 
+### Compilation of sources missing the debian/-directory
+
+The `debian` directory contains meta information on how to build a package from source. This is roughly speaking "configure", "compile", "install" all described in a Debian-specific way.
+Isar expects your sources to contain the `debian` folder and the above steps need to be described in it, not in a task in a recipe.
+
+So once you have sources you always need to combine them with a `debian` folder before Isar can build a package for you.
+You might be able to find a debianization for a component on the internet, i.e. Ubuntu does package an open source component while Debian does not. Your recipe could download the `debian` folder from Ubuntu and the sources from the open source project.
+
+You can write it yourself, which can be pretty easy but requires a bit of studying. <https://www.debian.org/doc/debian-policy/index.html>
+
+Isar does actually contain a helper that aims to "debianize" sources for your. If your package uses a build-system that Debian knows and follows the well known "configure", "compile", "install" scheme that debianization might just fit your needs without reading Debian manuals.
+If it does not fully fit your needs, it probably gives you a good starting point for your manual tuning.
+
+The shell function `deb_debianize` creates a `debian` folder. But it will not overwrite files that already are in WORKDIR. So you can either just call it to fully generate the `debian` folder. Or you combine it with pre-existing parts.
+
+Have a look at meta-isar/recipes-app/samefile/samefile_2.14.bb and meta/classes/debianize.bbclass for an example and the implementation.
+
 ### Packages without source
 
 If your customization is not about compiling from source there is a second way of creating `deb` packages. That way can be used for cases like:
diff --git a/meta-isar/recipes-app/samefile/samefile_2.14.bb b/meta-isar/recipes-app/samefile/samefile_2.14.bb
index a24d574..0ace85a 100644
--- a/meta-isar/recipes-app/samefile/samefile_2.14.bb
+++ b/meta-isar/recipes-app/samefile/samefile_2.14.bb
@@ -12,5 +12,19 @@ SRC_URI[md5sum] = "0b438249f3549f18b49cbb49b0473f70"
 
 do_prepare_build[cleandirs] += "${S}/debian"
 do_prepare_build() {
+    # you could also create parts of your debianization before
+    # pre-exisiting files will not be recreated
+    # 42 is not actually valid ... this is just a stupid example
+    echo 42 > "${WORKDIR}"/compat
+
+    # this step creates everything dpkg-buildpackage needs, compat will not be
+    # overwritten
     deb_debianize
+
+    # now if you are not happy you can post-process the result
+    # now let us "repair" the compat
+    echo 9 > "${S}/debian/compat"
+    # compat happens to be used by this step, so do that again
+    # see debianize.bbclass
+    deb_create_control
 }
diff --git a/meta/classes/debianize.bbclass b/meta/classes/debianize.bbclass
index fb9c234..e1c79ab 100644
--- a/meta/classes/debianize.bbclass
+++ b/meta/classes/debianize.bbclass
@@ -76,23 +76,29 @@ EOF
 }
 
 deb_debianize() {
+	# create the compat-file if there is no file with that name in WORKDIR
 	if [ -f ${WORKDIR}/compat ]; then
 		install -v -m 644 ${WORKDIR}/compat ${S}/debian/compat
 	else
 		deb_create_compat
 	fi
+	# create the control-file if there is no contro-file in WORKDIR
 	if [ -f ${WORKDIR}/control ]; then
 		install -v -m 644 ${WORKDIR}/control ${S}/debian/control
 	else
 		deb_create_control
 	fi
+	# create rules if WORKDIR does not contain a rules-file
 	if [ -f ${WORKDIR}/rules ]; then
 		install -v -m 755 ${WORKDIR}/rules ${S}/debian/rules
 	else
 		deb_create_rules
 	fi
+	# prepend a changelog-entry unless an existing changelog file already
+	# contains an entry with CHANGELOG_V
 	deb_add_changelog
 
+	# copy all hooks from WORKDIR into debian/, hooks are not generated
 	for t in pre post
 	do
 		for a in inst rm
-- 
2.23.0