phabricator: treat non-utf-8 text files as binary as phabricator requires

Phabricator can't cope with text files that are not UTF-8, so requires them to
be submitted as binary files instead.  This has the unfortunate effect of
making them practically unreviewable in Phabricator since it will only display
the separate versions of the file in other views, not a diff.  `phabread`ing
such submissions are similar, since it will just output the binary patch, but
`hg import` copes with it fine and `hg diff` afterwards will show the actual
changes.  It is still a marked improvement over trying to submit them as text,
which just leads to corruption (Phabricator will either output ? or HTML
entities for non-UTF-8 characters, depending on context).

Running decode on the whole file like this seems slightly unfortunate, but I'm
not aware of a better way.
Needs to be done to p1() version as well to detect conversions to UTF-8.

Differential Revision: https://phab.mercurial-scm.org/D7054

hgext/phabricator.py

@@ -697,6 +697,23 b' def makebinary(pchange, fctx):'
 gitmode = {b'l': b'120000', b'x': b'100755', b'': b'100644'}
 
 
+def notutf8(fctx):
+    """detect non-UTF-8 text files since Phabricator requires them to be marked
+    as binary
+    """
+    try:
+        fctx.data().decode('utf-8')
+        if fctx.parents():
+            fctx.p1().data().decode('utf-8')
+        return False
+    except UnicodeDecodeError:
+        fctx.repo().ui.write(
+            _(b'file %s detected as non-UTF-8, marked as binary\n')
+            % fctx.path()
+        )
+        return True
+
+
 def addremoved(pdiff, ctx, removed):
     """add removed files to the phabdiff. Shouldn't include moves"""
     for fname in removed:
@@ -705,7 +722,7 b' def addremoved(pdiff, ctx, removed):'
         )
         pchange.addoldmode(gitmode[ctx.p1()[fname].flags()])
         fctx = ctx.p1()[fname]
-        if not fctx.isbinary():
+        if not (fctx.isbinary() or notutf8(fctx)):
             maketext(pchange, ctx, fname)
 
         pdiff.addchange(pchange)
@@ -722,7 +739,7 b' def addmodified(pdiff, ctx, modified):'
             pchange.addoldmode(originalmode)
             pchange.addnewmode(filemode)
 
-        if fctx.isbinary():
+        if fctx.isbinary() or notutf8(fctx):
             makebinary(pchange, fctx)
             addoldbinary(pchange, fctx, fname)
         else:
@@ -781,7 +798,7 b' def addadded(pdiff, ctx, added, removed)'
             pchange.addnewmode(gitmode[fctx.flags()])
             pchange.type = DiffChangeType.ADD
 
-        if fctx.isbinary():
+        if fctx.isbinary() or notutf8(fctx):
             makebinary(pchange, fctx)
             if renamed:
                 addoldbinary(pchange, fctx, originalfname)