Derive -rc1 release-notes from a previous release branch.

The -rc1 candidate in an RNSeries will always track a snapshot
(per the rules in toNextCandidate()) and snapshots don't have
branches in the release-notes repository.  Subsequenct candidates
(-rc2, -rcN) (and releases) will track a previous candidate which
will have a branch in the release-notes repository.  For -rc1
candidate series we need to determine where to derive the
release-notes.

The -rc1 of the first GCC X.1 series needs to have the
release-notes derived from the template README.series.textile.
The -rc1 of subsequent series needs to have the release-notes
derived from the previous release in order to maintain
continuity of the release-notes across every series in the
GCC release.

We look to see if there is a previous release in the series
and if we don't find one we derive from the template.

Change-Id: I1c3d721d6c8a13763c9508d4d0bd49e7fc5c681f

5 files changed, 107 insertions, 28 deletions

diff --git a/linaropy/git/gitrepo.py b/linaropy/git/gitrepo.py
index 37333b3..69e47bb 100644
--- a/linaropy/git/gitrepo.py
+++ b/linaropy/git/gitrepo.py
@@ -61,6 +61,10 @@ class GitRepo(object):
                 return False
             return True
 
+    # See if the specified branch exists as a remote.
+    def remote_branch_exists(self, branch):
+        return self.branch_exists(self.remote_branchname(branch))
+
     def getbranch(self):
         try:
             with cd(self.repodir):
diff --git a/linaropy/rn/linaroseries.py b/linaropy/rn/linaroseries.py
index c8ea3e1..5c7f2ab 100644
--- a/linaropy/rn/linaroseries.py
+++ b/linaropy/rn/linaroseries.py
@@ -172,6 +172,15 @@ class LinaroSeries(Series):
     def toNext(self, seriestype, date=None, strict=False):
         return self.dispatchnext[seriestype](date, strict)
 
+    # This will return new LinaroSeries release from the previous month.
+    def toPreviousMonthsRelease(self):
+        prev_release = copy.deepcopy(self)
+        prev_release.seriestype = Series.series.index("release")
+        prev_release.spin.zero()
+        prev_release.rc.zero()
+        prev_release.date = self.date + relativedelta(months=-1)
+
+        return prev_release
 
 def linaro_series_from_tag(tag=None):
     series = series_from_tag(tag)
diff --git a/linaropy/rn/rnseries.py b/linaropy/rn/rnseries.py
index 247fb6b..87dacb8 100644
--- a/linaropy/rn/rnseries.py
+++ b/linaropy/rn/rnseries.py
@@ -141,25 +141,92 @@ class RNSeries(object):
             self.track_series.branchname())
         if not self.rn_series:
             logging.info("Looking for branch %s" % self.track_series.branchname())
-            # The workdir for the first candidate series will be derived from
-            # the changes made to the master branch templates.  The workdir for
-            # subsequent candidates and releases will be made based on the
-            # existing candidate or release branch.
+
+            # The -rc1 candidate in an RNSeries will always track a snapshot
+            # (per the rules in toNextCandidate()) and snapshots don't have
+            # branches in the release-notes repository.  Subsequenct candidates
+            # (-rc2, -rcN) (and releases) will track a previous candidate which
+            # will have a branch in the release-notes repository.  For -rc1
+            # candidate series we need to determine where to derive the
+            # release-notes.
             if not self.rn_clone.branch_exists(remote_track):
-                logging.info(
-                    "Creating RNSeries based on branch "
-                    + self.rn_template.getbranch())
+
+                # The -rc1 of the first GCC X.1 series needs to have the
+                # release-notes derived from the template README.series.textile.
+                # The -rc1 of subsequent series needs to have the release-notes
+                # derived from the previous release in order to maintain
+                # continuity of the release-notes across every series in the
+                # GCC release.
+
+                # We look to see if there is a previous release in the series
+                # and if we don't find one we derive from the template.
+
+                found_previous=None
+                prev_release = self.next_series
+                # Look two years back because that's the length of a supported
+                # release.
+                next_minor = self.next_series.package.version.minor
+                for x in xrange(1,25):
+
+                    # Search for the nearest previous release.  We need to
+                    # iterate through the minor variations blindly
+                    # (unfortunately) because the release process doesn't follow
+                    # a strict schedule with regard to date and minor number.
+                    prev_release=prev_release.toPreviousMonthsRelease()
+
+                    while True:
+                        try:
+                            logging.info("looking for previous release branch "
+                                "'%s'" % prev_release.branchname())
+                            if self.rn_clone.remote_branch_exists(
+                                    prev_release.branchname()):
+                                logging.info ("previous release branch "
+                                    "'%s' exists." % prev_release.branchname())
+                                found_previous=prev_release
+                                break
+
+                            prev_release.package.version.decrement_minor()
+                        except ValueError:
+                            break
+
+                    # Early exit if we've found a release.
+                    if found_previous:
+                        break
+
+                    # Restore the starting 'minor' for the next month.
+                    prev_release.package.version.minor=next_minor
+
+                if not found_previous:
+                    track=self.rn_template.getbranch()
+                    print_info(
+                        "Deriving your release-notes from template branch "
+                        "%s%s%s%s"
+                        % (BOLD, RED, track, NC))
+                else:
+
+                    # TODO: if we find a release series we need to increment the
+                    # spin an search for that branch to determine whether there
+                    # was a release respin.  Keep incrementing until we discover
+                    # no new spins and then we can select the previously
+                    # identified spin.
+                    logging.warning("Fixme: If the previous release had a spin "
+                        "we aren't yet able to detect it yet.")
+                    track=found_previous.branchname()
+                    print_info(
+                        "Deriving your release-notes from release branch "
+                        "%s%s%s%s"
+                        % (BOLD, RED, track, NC))
 
                 self.rn_series = Workdir(
                     proj=self.proj,
                     clone=self.rn_clone,
                     workdir=self.next_series.shorttype(),
-                    track=self.rn_template.getbranch(),
+                    track=track,
                     branchname=self.next_series.branchname())
             else:
-                logging.info(
-                    "Creating RNSeries based on branch "
-                    + remote_track)
+                print_info(
+                    "Deriving your release-notes from branch %s%s%s%s"
+                    % (BOLD, RED, track, NC))
 
                 self.rn_series = Workdir(
                     proj=self.proj,
@@ -168,19 +235,9 @@ class RNSeries(object):
                     track=remote_track,
                     branchname=self.next_series.branchname())
 
-                print_info(
-                    "  If you updated the template README.textile.series file"
-                    " the changes will not be reflected in this series")
-                print_info(
-                    "  README.textile.series as this series is derived from"
-                    " the %s%s%s%s" % (BOLD, RED, remote_track, NC))
-                print_info(
-                    "  series release notes.  Please make the changes to the"
-                    " series README.textile.series file as well.")
-
-                # TODO: Ask if the user would like to merge the changes in
-                # the template README.textile.series file instead of the
-                # long-winded warning above.
+        # TODO: Detect if the user changed the template README.textile or
+        # template README.textile.series and ask if they want to merge the
+        # changes into the new rn_series files.
 
         if not headless:
             answer = yninput(
@@ -189,6 +246,8 @@ class RNSeries(object):
             if answer == "y":
                 self.rn_series.edit(self._series)
 
+        # TODO: If there are multiple commits, the subsequent calls should use
+        # commit --amend.  Add an 'amend' parameter to GitRepo::commit().
         return self.rn_series.commit(
             "Added NEWS items for %s." % self.next_series.branchname())
 
diff --git a/linaropy/vers.py b/linaropy/vers.py
index 097181c..27fc0ce 100644
--- a/linaropy/vers.py
+++ b/linaropy/vers.py
@@ -105,9 +105,13 @@ class Version(object):
                 numtoks = numtoks - 1
         return vers
 
-# Helper function which returns a Version.
-
+    def decrement_minor(self):
+        if self.minor and self.minor >= 1:
+            self.minor = self.minor - 1
+        else:
+            raise ValueError("Minor must be greater than or equal to zero.")
 
+# Helper function which returns a Version.
 def versionFromStr(version):
     if not isinstance(version, basestring):
         raise TypeError('input must be of type basestring')
@@ -222,6 +226,9 @@ class Vers(object):
     def increment(self):
         self.val = self.val + 1
 
+    def zero(self):
+        self.val = 0
+
     # Return the "-<val>" string or an empty string.
     def __str__(self):
         # Don't return
diff --git a/rn.py b/rn.py
index 6de8ad9..2f64b1a 100644
--- a/rn.py
+++ b/rn.py
@@ -62,10 +62,10 @@ def generate(track, to_date, to_series, gccsource, persist):
     logging.info("fsf revision is " + gccclone.get_fsf_revision())
 
     if gccclone.tag_exists(track):
-        logging.info("%s is a tag.  Creating Series from tag.")
+        logging.info("%s is a tag.  Creating Series from tag." % track)
         track_series = linaro_series_from_tag(track)
     else:
-        logging.info("%s is a branch.  Creating Series from branchname.")
+        logging.info("%s is a branch.  Creating Series from branchname." % track)
         track_series = linaroSeriesFromBranchname(track)
 
     try: