hell, world! tutorial added

Author: gsell

src/Tutorials.adoc

@@ -1,3 +1,74 @@
 = *TUTORIALS*
 
+== Step-by-step guide to build a 'Hello, world!' module
+
+1. Download a stub for a new build-block
++
+[source,shell]
+----
+wget --output-document=stub.tgz https://github.com/Pmodules/buildblock_stub/archive/refs/tags/1.0.0.tar.gz 
+----
+1. Unpack the stub into the directory `hello_world`
++
+[source,shell]
+----
+mkdir hello_world
+tar --strip-components 1 -xvf ../stub.tgz
+chmod 0755 build
+----
+1. Edit `files/config.yaml`
++
+[source,yaml]
+----
+format: 1
+hello_world:                           # <1>
+  defaults:                            # <2>
+    group: Tools                       # <3>
+    relstage: stable                   # <4>
+    systems: [.*]                      # <5>
+    docfiles: [LICENSE]
+    compile_in_sourcetree: true        # <6>
+    urls:                              # <7>
+      - url: https://github.com/Pmodules/$P/archive/refs/tags/$V.tar.gz 
+        name: $P-$V.tar.gz
+
+  shasums:                             # <8>
+    hello_world-1.0.0.tar.gz: bc1cfd90ac55e9f3babab0a426ed4b3c7edf15266363ab1b595d234797fbce7b 
+
+  versions:
+    1.0.0:
+      config:                          # <9>
+        relstage: unstable             # <10>
+----
++
+<1> The name of the module.
+<2> Default configuration for all version. This can be overwritten in the 'versions' section.
+<3> The group the module will be installed in.
+<4> If not otherwise specified in the version specific configuration, the release stage is set to `stable`.
+<5> The module is available on all systems. Availability can be restricted to hostname patterns and/or OS/Linux distribution (like rhel8, sles15)
+<6> Usually the software is compiled in a dedicated build directory. Here we have to compile in the source tree.
+<7> Download URL and filename. `$P` will be substituted by the module name and `$V` by the version. 
+<8> SHA256 hash sums for each source file.
+<9> Configuration for version 1.0.0. 
+<10> Overwrite the default release stage.
+
+1. Edit the build script
++
+[source,shell]
+----
+#!/usr/bin/env modbuild
+
+pbuild::configure() {    # <1>
+	:
+}
+
+pbuild::install() {      # <2>
+	mkdir -p "${PREFIX}/bin"
+	install --mode=0755 "${SRC_DIR}/hello_world" "${PREFIX}/bin"
+}
+----
+<1> Don't use the default `pbuild::configure()`` function!
+    There is nothing to configure. :)
+<2> The Makefile doesn't have an 'install' target. Therefore we have to code it ourself. 
+