Use per-SCM node prefix letters instead of the general "n"

"Node" is an uncommon name for what SCMs usually call "revision", so the
"n" prefix is not very telling. Replace it with a prefix specific to the
SCM, so we actually also get to know with SCM is used.

Author: sschuberth

README.rst

@@ -114,11 +114,11 @@ and uses roughly the following logic to render the version:
 :code:`no distance and clean`:
     :code:`{tag}`
 :code:`distance and clean`:
-    :code:`{next_version}.dev{distance}+n{revision hash}`
+    :code:`{next_version}.dev{distance}+{scm letter}{revision hash}`
 :code:`no distance and not clean`:
     :code:`{tag}+dYYYMMMDD`
 :code:`distance and not clean`:
-    :code:`{next_version}.dev{distance}+n{revision hash}.dYYYMMMDD`
+    :code:`{next_version}.dev{distance}+{scm letter}{revision hash}.dYYYMMMDD`
 
 The next version is calculated by adding ``1`` to the last numeric component
 of the tag.

setuptools_scm/hg.py

@@ -7,7 +7,7 @@
 
 def _hg_tagdist_normalize_tagcommit(root, tag, dist, node):
     dirty = node.endswith('+')
-    node = node.strip('+')
+    node = 'h' + node.strip('+')
     revset = ("(branch(.) and tag({tag!r})::. and file('re:^(?!\.hgtags).*$')"
               " - tag({tag!r}))").format(tag=tag)
     if tag != '0.0':
@@ -58,14 +58,17 @@ def parse(root):
 
 def archival_to_version(data):
     trace('data', data)
+    node = data.get('node', '')[:12]
+    if node:
+        node = 'h' + node
     if 'tag' in data:
         return meta(data['tag'])
     elif 'latesttag' in data:
         return meta(data['latesttag'],
                     distance=data['latesttagdistance'],
-                    node=data['node'][:12])
+                    node=node)
     else:
-        return meta('0.0', node=data.get('node', '')[:12])
+        return meta('0.0', node=node)
 
 
 def parse_archival(root):

setuptools_scm/version.py

@@ -125,7 +125,7 @@ def get_local_node_and_date(version):
     if version.exact or version.node is None:
         return version.format_choice("", "+d{time:%Y%m%d}")
     else:
-        return version.format_choice("+n{node}", "+n{node}.d{time:%Y%m%d}")
+        return version.format_choice("+{node}", "+{node}.d{time:%Y%m%d}")
 
 
 def get_local_dirty_tag(version):

testing/test_git.py

@@ -19,17 +19,17 @@ def test_version_from_git(wd):
     assert wd.version == '0.1.dev0'
 
     wd.commit_testfile()
-    assert wd.version.startswith('0.1.dev1+')
+    assert wd.version.startswith('0.1.dev1+g')
     assert not wd.version.endswith('1-')
 
     wd('git tag v0.1')
     assert wd.version == '0.1'
 
     wd.write('test.txt', 'test2')
-    assert wd.version.startswith('0.2.dev0+')
+    assert wd.version.startswith('0.2.dev0+g')
 
     wd.commit_testfile()
-    assert wd.version.startswith('0.2.dev1+')
+    assert wd.version.startswith('0.2.dev1+g')
 
     wd('git tag version-0.2')
     assert wd.version.startswith('0.2')
@@ -101,4 +101,4 @@ def test_parse_no_worktree(tmpdir):
 def test_alphanumeric_tags_match(wd):
     wd.commit_testfile()
     wd('git tag newstyle-development-started')
-    assert wd.version.startswith('0.1.dev1+')
+    assert wd.version.startswith('0.1.dev1+g')

testing/test_mercurial.py

@@ -15,7 +15,7 @@ def wd(wd):
 
 archival_mapping = {
     '1.0': {'tag': '1.0'},
-    '1.1.dev3+n000000000000': {
+    '1.1.dev3+h000000000000': {
         'latesttag': '1.0',
         'latesttagdistance': '3',
         'node': '0'*20,
@@ -91,7 +91,7 @@ def test_version_from_archival(wd):
         'latesttagdistance: 3\n'
     )
 
-    assert wd.version == '0.2.dev3+n000000000000'
+    assert wd.version == '0.2.dev3+h000000000000'
 
 
 @pytest.mark.issue('#72')