Set up pre-commit hook for clang-format

.clang-format

@@ -0,0 +1,72 @@
+---
+Language:        Cpp
+BasedOnStyle:  Microsoft
+
+# Indentation
+IndentWidth: 2                    # 2 spaces per indent
+AccessModifierOffset: -2
+IndentAccessModifiers: false      # Align access modifiers to braces
+NamespaceIndentation: All       # Indent namspace contents
+ConstructorInitializerIndentWidth: 2
+
+# Comments which match this regex will be unformatted (and therefore can be longer or have more whitespace than other comments)
+CommentPragmas: '^\*\*'
+
+
+# Alignment
+AlignConsecutiveAssignments:
+  Enabled:          true
+  AcrossEmptyLines: false
+  AcrossComments:   true
+  AlignCompound:    true
+  PadOperators:     true
+AlignConsecutiveBitFields:
+  Enabled:          true
+  AcrossEmptyLines: false
+  AcrossComments:   true
+AlignConsecutiveDeclarations:
+  Enabled:          true
+  AcrossEmptyLines: false
+  AcrossComments:   true
+  # For future versions of clang-format
+  # AlignFunctionDeclarations: false
+  # AlignFunctionPointers: false
+AlignConsecutiveMacros:
+  Enabled:          true
+  AcrossEmptyLines: false
+  AcrossComments:   true
+
+# Newlines
+ColumnLimit:     0
+BreakBeforeBraces: Allman         # Braces on their own lines
+SeparateDefinitionBlocks: Always  # Separate definitions (functions etc.) with an empty line
+AlwaysBreakTemplateDeclarations: true # Put template on their own lines
+AllowShortBlocksOnASingleLine: Never
+# On a newer version of clang-format, replace with BinPackArguments: OnePerLine
+BinPackArguments: false           # Don't allow multiple function arguments on the same line unless they all fit
+BinPackParameters: false          # Same but for parameters
+PackConstructorInitializers: NextLine
+AllowShortFunctionsOnASingleLine: None
+BreakBeforeBinaryOperators: NonAssignment # Put binary operators after a line break, rather than before
+AllowShortIfStatementsOnASingleLine: Never
+
+# Spaces
+SpaceBeforeParens: ControlStatementsExceptControlMacros
+SpaceAfterCStyleCast: true
+PointerAlignment: Left
+
+# Includes
+IncludeBlocks: Regroup            # Regroup includes based on config
+IncludeCategories:
+  - Regex:           '(^"|\.hpp)'  # 'local' includes
+    Priority:        3
+    SortPriority:    0
+    CaseSensitive:   false
+  - Regex:           '\/'         # Library includes
+    Priority:        2
+    SortPriority:    0
+    CaseSensitive:   false
+  - Regex:           '.*'         # Everything else
+    Priority:        1
+    SortPriority:    0
+    CaseSensitive:   false

.github/workflows/pre_commit.yaml

@@ -0,0 +1,22 @@
+name: gridkit-bot pre-commit
+
+# Won't run on develop/main directly
+on: [pull_request]
+
+jobs:
+  pre-commit:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        ref: ${{ github.event.pull_request.head.ref }}
+    - uses: actions/[email protected]
+    - uses: pre-commit/[email protected]
+    - uses: EndBug/[email protected]
+      # Only need to try and commit if the action failed
+      if: failure()
+      with:
+        fetch: false
+        committer_name: GitHub Actions
+        committer_email: [email protected]
+        message: Apply pre-commmit fixes 

.gitignore

@@ -4,4 +4,4 @@
 .vscode/
 *.DS_Store
 build/
-*.DS_Store
+*.DS_Store

.pre-commit-config.yaml

@@ -0,0 +1,12 @@
+repos:
+  - repo: https://github.com/pre-commit/mirrors-clang-format
+    rev: v19.1.7
+    hooks:
+    - id: clang-format
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v5.0.0
+    hooks:
+    - id: check-toml
+    - id: forbid-new-submodules
+    - id: end-of-file-fixer
+    - id: check-yaml

CONTRIBUTING.md

@@ -30,6 +30,25 @@ Each class should be implemented in a `*.cpp` and a `*.hpp` files with
 the same name. Files containing collection of standalone functions should
 have a descriptive name starting with lowercase character.
 
+### Using `clang-format`
+
+Coding style rules are specified in `.clang-format` file in GridKit root
+directory. Use
+```shell
+clang-format -i <filename>
+```
+to make sure your code follows the style guidelines.
+
+### Line length
+
+Keep line length below 80 characters unless a longer line is needed for better
+clarity of the code. If your line is longer than 90 characters, you are
+probably doing something wrong.
+
+`clang-format` is configured so it does not enforce line length; that is
+developer's responsibility. Break the long lines at places where it will
+improve readability of the code. Running `clang-format` after that will help
+align the code properly in accordance with GridKit coding style.
 
 ### Local variables naming
 
@@ -98,10 +117,10 @@ constants with long names, use underscores to separate words in the constant
 name. Use all caps (screaming snake case).
 
 ```c++
-   constexpr double Pi = 3.1415; // No, the constant name should be all caps
+   constexpr double Pi = 3.1415;      // No, use all caps for the constant name
    constexpr double SQRT_TWO = 1.4142 // Yes
-   constexpr double SQRTTWO_ = 1.4142 // No, there is a trailing underscore
-   constexpr double EXP = 2.7183 // Yes   
+   constexpr double SQRTTWO = 1.4142  // No, the two words not separated by "_"
+   constexpr double EXP = 2.7183      // Yes 
 ```
 
 ### Pointers and references
@@ -115,7 +134,7 @@ int & n;       // No, the reference symbol is a part of `int&` type
 ```
 
 ### Indentation
-Use only spaces for indentation, not tabs. Indent size is 4 spaces.
+Use only spaces for indentation, not tabs. Indent size is 2 spaces.
 
 When defining a class, the code blocks after `private`, `public` and `protected`
 should be aligned with opening/closing braces. There should be an empty line
@@ -138,7 +157,7 @@ protected:
 ### Braces
 All braces should follow Allman style:
 ```c++
-namespace someNamespace
+namespace SomeNamespace
 {
   //some code 
 }
@@ -321,4 +340,3 @@ class Matrix   // No, class is outside GridKit namespace
 {
   // matrix code
 };
-