Add MarkdownfmtBear

It suggests better formatting in markdown files.

Closes coala#1538

.ci/deps.sh

@@ -19,6 +19,7 @@ go get -u sourcegraph.com/sqs/goreturns
 go get -u golang.org/x/tools/cmd/gotype
 go get -u github.com/kisielk/errcheck
 go get -u github.com/BurntSushi/toml/cmd/tomlv
+go get -u github.com/shurcooL/markdownfmt
 
 # Ruby commands
 bundle install --path=vendor/bundle --binstubs=vendor/bin --jobs=8 --retry=3

bears/markdown/MarkdownfmtBear.py

@@ -0,0 +1,28 @@
+from coalib.bearlib.abstractions.Linter import linter
+from dependency_management.requirements.GoRequirement import GoRequirement
+
+
+@linter(executable='markdownfmt',
+        output_format='corrected',
+        result_message='Formatting can be improved.',
+        use_stdin=True)
+class MarkdownfmtBear:
+    """
+    Check and correct formatting of Markdown files using ``mardownfmt``.
+    Basic checks like alignment, indendation are provided.
+    Note that MarkdownfmtBear works only with pure Markdown files(shouldn't
+    contain front matter like TOML, JS etc).
+    """
+    LANGUAGES = {'Markdown'}
+    REQUIREMENTS = {GoRequirement(
+                     package='github.com/shurcooL/markdownfmt')}
+    AUTHORS = {'The coala developers'}
+    AUTHORS_EMAILS = {'[email protected]'}
+    LICENSE = 'AGPL-3.0'
+    CAN_FIX = {'Formatting'}
+    ASCIINEMA_URL = 'https://asciinema.org/a/396jhuyw1j0c1l2i9p09wlhye'
+    SEE_MORE = 'https://github.com/shurcooL/markdownfmt'
+
+    @staticmethod
+    def create_arguments(filename, file, config_file):
+        return list()

tests/markdown/MarkdownfmtBearTest.py

@@ -0,0 +1,33 @@
+from coalib.testing.LocalBearTestHelper import verify_local_bear
+
+from bears.markdown.MarkdownfmtBear import MarkdownfmtBear
+
+
+header_in_file1 = """
+MarkdownBear
+=====
+
+"""
+
+header_out_file1 = """
+MarkdownBear
+============
+
+"""
+
+spacing_in_file2 = """
+
+This is   a test    file.
+
+"""
+
+spacing_out_file2 = """
+
+This is a test file.
+
+"""
+
+MarkdownfmtBear = verify_local_bear(
+    MarkdownfmtBear,
+    valid_files=(header_in_file1, spacing_in_file2,),
+    invalid_files=(header_out_file1, spacing_out_file2,))