global: make some docstrings raw strings

Python 3.8 emits a SyntaxWarning when a str/bytes contains invalid
\ escapes. Various docstrings in our code base contain invalid
\ escapes.

This commit turns those docstrings into raw strings.

Differential Revision: https://phab.mercurial-scm.org/D5816

hgext/rebase.py

@@ -1278,7 +1278,7 b' def rebasenode(repo, rev, p1, base, coll'
     return stats
 
 def adjustdest(repo, rev, destmap, state, skipped):
-    """adjust rebase destination given the current rebase state
+    r"""adjust rebase destination given the current rebase state
 
     rev is what is being rebased. Return a list of two revs, which are the
     adjusted destinations for rev's p1 and p2, respectively. If a parent is

mercurial/bookmarks.py

@@ -44,7 +44,7 b' def _getbkfile(repo):'
     return fp
 
 class bmstore(object):
-    """Storage for bookmarks.
+    r"""Storage for bookmarks.
 
     This object should do all bookmark-related reads and writes, so
     that it's fairly simple to replace the storage underlying

mercurial/dagop.py

@@ -142,7 +142,7 b' def _genrevancestors(repo, revs, followf'
 
 def revancestors(repo, revs, followfirst=False, startdepth=None,
                  stopdepth=None, cutfunc=None):
-    """Like revlog.ancestors(), but supports additional options, includes
+    r"""Like revlog.ancestors(), but supports additional options, includes
     the given revs themselves, and returns a smartset
 
     Scan ends at the stopdepth (exlusive) if specified. Revisions found

setup.py

@@ -666,7 +666,7 b' class buildhgexe(build_ext):'
             self.addlongpathsmanifest()
 
     def addlongpathsmanifest(self):
-        """Add manifest pieces so that hg.exe understands long paths
+        r"""Add manifest pieces so that hg.exe understands long paths
 
         This is an EXPERIMENTAL feature, use with care.
         To enable long paths support, one needs to do two things: