[v2] Honour BB_FETCH_PREMIRRORONLY option

diff --git a/lib/bb/fetch2/__init__.py b/lib/bb/fetch2/__init__.py
index 5dfe5ff3..ce013eb2 100644
--- a/lib/bb/fetch2/__init__.py
+++ b/lib/bb/fetch2/__init__.py
@@ -1744,6 +1744,8 @@  class Fetch(object):
                             done = False
 
                 if premirroronly:
+                    if not done:
+                        raise FetchError("Failed to download premirror {} and BB_FETCH_PREMIRRORONLY has been set to 1.".format(self.d.getVar("PREMIRRORS")))
                     self.d.setVar("BB_NO_NETWORK", "1")
 
                 firsterr = None
diff --git a/lib/bb/fetch2/git.py b/lib/bb/fetch2/git.py
index 4d06a571..0d5f6048 100644
--- a/lib/bb/fetch2/git.py
+++ b/lib/bb/fetch2/git.py
@@ -335,11 +335,7 @@  class Git(FetchMethod):
     def try_premirror(self, ud, d):
         # If we don't do this, updating an existing checkout with only premirrors
         # is not possible
-        if bb.utils.to_boolean(d.getVar("BB_FETCH_PREMIRRORONLY")):
-            return True
-        if os.path.exists(ud.clonedir):
-            return False
-        return True
+        return bb.utils.to_boolean(d.getVar("BB_FETCH_PREMIRRORONLY")) or not os.path.exists(ud.clonedir)
 
     def download(self, ud, d):
         """Fetch url"""
@@ -350,10 +346,14 @@  class Git(FetchMethod):
         if ud.shallow and os.path.exists(ud.fullshallow) and self.need_update(ud, d):
             ud.localpath = ud.fullshallow
             return
-        elif os.path.exists(ud.fullmirror) and not os.path.exists(ud.clonedir):
-            bb.utils.mkdirhier(ud.clonedir)
-            runfetchcmd("tar -xzf %s" % ud.fullmirror, d, workdir=ud.clonedir)
-
+        if os.path.exists(ud.fullmirror):
+            if self.try_premirror(ud, d) and self.need_update(ud, d):
+                bb.utils.mkdirhier(ud.clonedir)
+                runfetchcmd("tar -xzf %s" % ud.fullmirror, d, workdir=ud.clonedir)
+                if self.need_update(ud, d) and \
+                   bb.utils.to_boolean(d.getVar("BB_FETCH_PREMIRRORONLY")):
+                    raise bb.fetch2.FetchError("Premirror doesn't contain revisions {} and "\
+                            "upstream cannot be used due to BB_FETCH_PREMIRRORONLY setting".format(ud.revisions))
         repourl = self._get_repo_url(ud)
 
         # If the repo still doesn't exist, fallback to cloning it
diff --git a/lib/bb/tests/fetch.py b/lib/bb/tests/fetch.py
index 233ecae7..62c7296e 100644
--- a/lib/bb/tests/fetch.py
+++ b/lib/bb/tests/fetch.py
@@ -2800,3 +2800,66 @@  class GitSharedTest(FetcherTest):
         fetcher.unpack(self.unpackdir)
         alt = os.path.join(self.unpackdir, 'git/.git/objects/info/alternates')
         self.assertFalse(os.path.exists(alt))
+
+
+class FetchPremirroronlyLocalTest(FetcherTest):
+
+    def git(self, cmd, cwd=None):
+        if isinstance(cmd, str):
+            cmd = 'git ' + cmd
+        else:
+            cmd = ['git'] + cmd
+        if cwd is None:
+            cwd = self.gitdir
+        return bb.process.run(cmd, cwd=cwd)[0]
+
+    def setUp(self):
+        super(FetchPremirroronlyLocalTest, self).setUp()
+        self.mirrordir = os.path.join(self.tempdir, "mirrors")
+        os.mkdir(self.mirrordir)
+        self.reponame = "bitbake"
+        self.gitdir = os.path.join(self.tempdir, "git", self.reponame)
+        self.recipe_url = "git://git.fake.repo/bitbake"
+        self.d.setVar("BB_FETCH_PREMIRRORONLY", "1")
+        self.d.setVar("BB_NO_NETWORK", "1")
+        self.d.setVar("PREMIRRORS", self.recipe_url + " " + "file://{}".format(self.mirrordir) + " \n")
+
+    def make_git_repo(self):
+        self.mirrorname = "git2_git.fake.repo.bitbake.tar.gz"
+        recipeurl = "git:/git.fake.repo/bitbake"
+        os.makedirs(self.gitdir)
+        self.git("init", self.gitdir)
+        for i in range(0):
+            self.git_new_commit()
+        bb.process.run('tar -czvf {} .'.format(os.path.join(self.mirrordir, self.mirrorname)), cwd =  self.gitdir)
+
+    def git_new_commit(self):
+        import random
+        testfilename = "bibake-fetch.test"
+        os.unlink(os.path.join(self.mirrordir, self.mirrorname))
+        with open(os.path.join(self.gitdir, testfilename), "w") as testfile:
+            testfile.write("Useless random data {}".format(random.random()))
+        self.git("add {}".format(testfilename), self.gitdir)
+        self.git("commit -a -m \"This random commit {}. I'm useless.\"".format(random.random()), self.gitdir)
+        bb.process.run('tar -czvf {} .'.format(os.path.join(self.mirrordir, self.mirrorname)), cwd =  self.gitdir)
+        return self.git("rev-parse HEAD", self.gitdir).strip()
+
+    def test_mirror_commit_nonexistent(self):
+        self.make_git_repo()
+        self.d.setVar("SRCREV", "0"*40)
+        fetcher = bb.fetch.Fetch([self.recipe_url], self.d)
+        with self.assertRaises(bb.fetch2.FetchError):
+            fetcher.download()
+
+    def test_mirror_commit_exists(self):
+        self.make_git_repo()
+        self.d.setVar("SRCREV", self.git_new_commit())
+        fetcher = bb.fetch.Fetch([self.recipe_url], self.d)
+        fetcher.download()
+        fetcher.unpack(self.unpackdir)
+
+    def test_mirror_tarball_nonexistent(self):
+        self.d.setVar("SRCREV", "0"*40)
+        fetcher = bb.fetch.Fetch([self.recipe_url], self.d)
+        with self.assertRaises(bb.fetch2.FetchError):
+            fetcher.download()