pipeline: detect host instead of using org.osbuild.host

Detect the host dynamically from os-release(5) instead of relying on the
`org.osbuild.host` symlink.

It is awkward to install a symlink that tells osbuild which distro is is
running on, when there is a standard way to detect this.

This makes it easier to run osbuild from sources and removes the need to
include every host in the spec file. The latter became hard to do,
because there's no obvious way to distinguish RHEL minor releases.

.gitignore

@@ -10,8 +10,6 @@ __pycache__
 
 /test/.vagrant
 
-/runners/org.osbuild.host
-
 /.vscode
 /.idea
 /.gdb_history

osbuild.spec

@@ -70,23 +70,6 @@ install -p -m 0755 $(find sources -type f) %{buildroot}%{pkgdir}/sources
 mkdir -p %{buildroot}%{pkgdir}/stages/osbuild
 mkdir -p %{buildroot}%{pkgdir}/assemblers/osbuild
 
-# install host runner
-%if 0%{?fc30}
-ln -s org.osbuild.fedora30 %{buildroot}%{pkgdir}/runners/org.osbuild.host
-%endif
-%if 0%{?fc31}
-ln -s org.osbuild.fedora31 %{buildroot}%{pkgdir}/runners/org.osbuild.host
-%endif
-%if 0%{?fc32}
-ln -s org.osbuild.fedora32 %{buildroot}%{pkgdir}/runners/org.osbuild.host
-%endif
-%if 0%{?fc33}
-ln -s org.osbuild.fedora33 %{buildroot}%{pkgdir}/runners/org.osbuild.host
-%endif
-%if 0%{?el8}
-ln -s org.osbuild.rhel82 %{buildroot}%{pkgdir}/runners/org.osbuild.host
-%endif
-
 %check
 exit 0
 # We have some integration tests, but those require running a VM, so that would

osbuild/pipeline.py

@@ -314,6 +314,33 @@ class Pipeline:
         return results
 
 
+def detect_os(*paths):
+    """Detect the os from an os-release file.
+
+    The first file in 'paths' is used and interpreted like a os-release(5)
+    file.
+
+    Returns ID + VERSION_ID (without dots), which is the same format that
+    runners are named as.
+    """
+    path = next((p for p in paths if os.path.exists(p)), None)
+    if not path:
+        raise FileNotFoundError("none of the specified os-release files exist")
+
+    with open(path) as f:
+        osrelease = {}
+        for line in f:
+            line = line.strip()
+            if not line:
+                continue
+            if line[0] == "#":
+                continue
+            key, value = line.split("=", 1)
+            osrelease[key] = value.strip('"')
+
+    return osrelease["ID"] + osrelease["VERSION_ID"].replace(".", "")
+
+
 def load_build(description, sources_options):
     pipeline = description.get("pipeline")
     if pipeline:
@@ -329,7 +356,7 @@ def load(description, sources_options):
     if build:
         build_pipeline, runner = load_build(build, sources_options)
     else:
-        build_pipeline, runner = None, "org.osbuild.host"
+        build_pipeline, runner = None, "org.osbuild." + detect_os("/etc/os-release", "/usr/lib/os-release")
 
     pipeline = Pipeline(runner, build_pipeline)