[autobuilder,2/2] scripts/send-qa-email: Generate regression reports against most relevant release

diff --git a/scripts/send-qa-email b/scripts/send-qa-email
index c2c5a4b..c2bdeb5 100755
--- a/scripts/send-qa-email
+++ b/scripts/send-qa-email
@@ -49,6 +49,54 @@  if os.path.exists(buildtoolsdir):
 
 repodir = os.path.dirname(args.repojson) + "/build/repos"
 
+def get_previous_tag(targetrepodir, version):
+    previousversion = None
+    previousmilestone = None
+    if version:
+        compareversion, comparemilestone, _ = utils.get_version_from_string(version)
+        print(f"Searching before {compareversion}")
+        compareversionminor = compareversion[-1]
+        # After ignoring rc part, if we get a minor to 0 on point release (e.g 4.0.0),
+        # reject last digit since such versions do not exist
+        if len(compareversion) == 3 and compareversionminor == 0:
+            compareversion = compareversion[:-1]
+
+        # Process milestone if not first in current release
+        if comparemilestone and comparemilestone > 1:
+            previousversion = compareversion
+            previousmilestone = comparemilestone-1
+        # Process first milestone or release if not first in major release
+        elif compareversionminor > 0:
+            previousversion = compareversion[:-1] + [compareversion[-1] - 1]
+        # Otherwise : format it as tag (which must exist) and search previous tag
+        else:
+            comparetagstring = utils.get_tag_from_version(compareversion, comparemilestone)
+            return subprocess.check_output(["git", "describe", "--abbrev=0", comparetagstring + "^"], cwd=targetrepodir).decode('utf-8').strip()
+
+        return utils.get_tag_from_version(previousversion, previousmilestone)
+
+    # All other cases : merely check against latest tag reachable
+    defaultbaseversion, _, _ = utils.get_version_from_string(subprocess.check_output(["git", "describe", "--abbrev=0"], cwd=targetrepodir).decode('utf-8').strip())
+    return utils.get_tag_from_version(defaultbaseversion, None)
+
+def get_sha1(targetrepodir, revision):
+    return subprocess.check_output(["git", "rev-list", "-n", "1", revision], cwd=targetrepodir).decode('utf-8').strip()
+
+def generate_regression_report(targetrepodir, basebranch, resultdir, yoctoversion):
+    baseversion = get_previous_tag(targetrepodir, yoctoversion)
+    baserevision = get_sha1(targetrepodir, baseversion)
+    comparerevision = get_sha1(targetrepodir, basebranch)
+    print(f"Compare version : {basebranch} ({comparerevision})")
+    print(f"Base tag : {baseversion} ({baserevision})")
+
+    try:
+        regreport = subprocess.check_output([resulttool, "regression-git", "-B", basebranch, "--commit", baserevision, "--commit2", comparerevision, resultdir])
+        with open(args.results_dir + "/testresult-regressions-report.txt", "wb") as f:
+           f.write(regreport)
+    except subprocess.CalledProcessError as e:
+        error = str(e)
+        print(f"Error while generating report between {baserevision} and {comparerevision} : {error}")
+
 if 'poky' in repos and os.path.exists(resulttool) and args.results_dir:
     # Need the finalised revisions (not 'HEAD')
     targetrepodir = "%s/poky" % (repodir)
@@ -56,16 +104,7 @@  if 'poky' in repos and os.path.exists(resulttool) and args.results_dir:
     branch = repos['poky']['branch']
     repo = repos['poky']['url']
 
-    extraopts = None
     basebranch, comparebranch = utils.getcomparisonbranch(ourconfig, repo, branch)
-    if basebranch:
-        extraopts = " --branch %s --commit %s" % (branch, revision)
-    if comparebranch:
-        extraopts = extraopts + " --branch2 %s" % (comparebranch)
-    elif basebranch:
-        print("No comparision branch found, comparing to %s" % basebranch)
-        extraopts = extraopts + " --branch2 %s" % basebranch
-
     report = subprocess.check_output([resulttool, "report", args.results_dir])
     with open(args.results_dir + "/testresult-report.txt", "wb") as f:
         f.write(report)
@@ -94,8 +133,6 @@  if 'poky' in repos and os.path.exists(resulttool) and args.results_dir:
                 subprocess.check_call(["git", "checkout", "master"], cwd=tempdir)
                 subprocess.check_call(["git", "branch", basebranch], cwd=tempdir)
                 subprocess.check_call(["git", "checkout", basebranch], cwd=tempdir)
-                extraopts = None
-
         subprocess.check_call([resulttool, "store", args.results_dir, tempdir])
         if comparebranch:
             subprocess.check_call(["git", "push", "--all", "--force"], cwd=tempdir)
@@ -104,10 +141,8 @@  if 'poky' in repos and os.path.exists(resulttool) and args.results_dir:
             subprocess.check_call(["git", "push", "--all"], cwd=tempdir)
             subprocess.check_call(["git", "push", "--tags"], cwd=tempdir)
 
-        if extraopts:
-            regreport = subprocess.check_output([resulttool, "regression-git", tempdir] + extraopts.split())
-            with open(args.results_dir + "/testresult-regressions-report.txt", "wb") as f:
-                f.write(regreport)
+        if basebranch:
+            generate_regression_report(targetrepodir, basebranch, tempdir, args.release)
 
     finally:
         subprocess.check_call(["rm", "-rf",  tempdir])
diff --git a/scripts/utils.py b/scripts/utils.py
index c0ad14e..444b3ab 100644
--- a/scripts/utils.py
+++ b/scripts/utils.py
@@ -478,3 +478,50 @@  def setup_buildtools_tarball(ourconfig, workername, btdir, checkonly=False):
                     pass
             subprocess.check_call(["bash", btdlpath, "-d", btdir, "-y"])
         enable_buildtools_tarball(btdir)
+
+def get_string_from_version(version, milestone=None, rc=None):
+    """ Point releases finishing by 0 (e.g 4.0.0, 4.1.0) do no exists,
+    those are major releases
+    """
+    if len(version) == 3 and version[-1] == 0:
+        version = version[:-1]
+
+    result = ".".join(list(map(str, version)))
+    if milestone:
+        result += "_M" + str(milestone)
+    if rc:
+        result += ".rc" + str(rc)
+    return result
+
+def get_tag_from_version(version, milestone):
+    if not milestone:
+        return "yocto-" + get_string_from_version(version, milestone)
+    return get_string_from_version(version, milestone)
+
+
+def get_version_from_string(raw_version):
+    """ Get version as list of int from raw_version.
+
+    Raw version _can_ be prefixed by "yocto-",
+    Raw version _can_ be suffixed by "_MX"
+    Raw version _can_ be suffixed by ".rcY"
+    """
+    version = None
+    milestone = None
+    rc = None
+    if raw_version[:6] == "yocto-":
+        raw_version = raw_version[6:]
+    raw_version = raw_version.split(".")
+    if raw_version[-1][:2] == "rc":
+        rc = int(raw_version[-1][-1])
+        raw_version = raw_version[:-1]
+    if raw_version[-1][-3:-1] == "_M":
+        milestone = int(raw_version[-1][-1])
+        raw_version = raw_version[:-1] + [raw_version[-1][:-3]]
+    version = list(map(int, raw_version))
+    """ Point releases finishing by 0 (e.g 4.0.0, 4.1.0) do no exists,
+    those are major releases
+    """
+    if len(version) == 3 and version[-1] == 0:
+        version = version[:-1]
+    return version, milestone, rc
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