Fix alignments in github tables

Closes #53, follow-up on #261

Author: kdeldycke

README.md

@@ -233,12 +233,12 @@ bacon       0
 ```
 
 `github` follows the conventions of GitHub flavored Markdown. It
-corresponds to the `pipe` format without alignment colons:
+corresponds to the `pipe` format with the same alignment colons:
 
 ```pycon
 >>> print(tabulate(table, headers, tablefmt="github"))
 | item   |   qty |
-|--------|-------|
+|:-------|------:|
 | spam   |    42 |
 | eggs   |   451 |
 | bacon  |     0 |

tabulate/__init__.py

@@ -522,16 +522,6 @@ def escape_empty(val):
         padding=1,
         with_header_hide=None,
     ),
-    "github": TableFormat(
-        lineabove=Line("|", "-", "|", "|"),
-        linebelowheader=Line("|", "-", "|", "|"),
-        linebetweenrows=None,
-        linebelow=None,
-        headerrow=DataRow("|", "|", "|"),
-        datarow=DataRow("|", "|", "|"),
-        padding=1,
-        with_header_hide=["lineabove"],
-    ),
     "pipe": TableFormat(
         lineabove=_pipe_line_with_colons,
         linebelowheader=_pipe_line_with_colons,
@@ -719,6 +709,10 @@ def escape_empty(val):
     ),
 }
 
+# "github" is an alias for "pipe": both produce GitHub-flavored Markdown with
+# alignment colons in the separator row.
+_table_formats["github"] = _table_formats["pipe"]
+
 
 tabulate_formats = sorted(_table_formats.keys())
 

test/test_output.py

@@ -369,9 +369,9 @@ def test_simple_headerless_with_sep_line_with_padding_in_tablefmt():
     "Output: simple without headers with sep line with padding in tablefmt"
     expected = "\n".join(
         [
-            "|------|----------|",
+            "|:-----|---------:|",
             "| spam |  41.9999 |",
-            "|------|----------|",
+            "|:-----|---------:|",
             "| eggs | 451      |",
         ]
     )
@@ -489,7 +489,7 @@ def test_github():
     expected = "\n".join(
         [
             "| strings   |   numbers |",
-            "|-----------|-----------|",
+            "|:----------|----------:|",
             "| spam      |   41.9999 |",
             "| eggs      |  451      |",
         ]
@@ -506,7 +506,7 @@ def test_github_multiline():
         [
             "|        more | more spam   |",
             "|   spam eggs | & eggs      |",
-            "|-------------|-------------|",
+            "|------------:|:------------|",
             "|           2 | foo         |",
             "|             | bar         |",
         ]
@@ -515,6 +515,45 @@ def test_github_multiline():
     assert_equal(expected, result)
 
 
+def test_github_with_colalign():
+    "Output: github with explicit column alignment"
+    expected = "\n".join(
+        [
+            "| Name   |   Age |",
+            "|:-------|------:|",
+            "| Alice  |    24 |",
+            "| Bob    |    19 |",
+        ]
+    )
+    result = tabulate(
+        [["Alice", 24], ["Bob", 19]],
+        ["Name", "Age"],
+        tablefmt="github",
+        colalign=("left", "right"),
+    )
+    assert_equal(expected, result)
+
+
+def test_github_no_alignment():
+    "Output: github without alignment hints when numalign/stralign are disabled"
+    expected = "\n".join(
+        [
+            "| strings | numbers |",
+            "|-----------|-----------|",
+            "| spam | 41.9999 |",
+            "| eggs | 451 |",
+        ]
+    )
+    result = tabulate(
+        _test_table,
+        _test_table_headers,
+        tablefmt="github",
+        numalign=None,
+        stralign=None,
+    )
+    assert_equal(expected, result)
+
+
 def test_grid():
     "Output: grid with headers"
     expected = "\n".join(