Add a pre-commit script and an adapted formatting file (#1534)

* Add a pre-commit script and an adapted formatting file

* Formatting

I am aware of the irony

* Fix typo

* Added documentation

* Fix Typo

docs/src/styleguide.md

@@ -65,3 +65,14 @@ utils/trixi-format.jl
 ```
 You can get more information about using the convenience script by running it with the
 `--help`/`-h` flag.
+
+### Checking formatting before committing
+It can be convenient to check the formatting of source code automatically before each commit. 
+We use git-hooks for it and provide a `pre-commit` script in the `utils` folder. The script uses
+[JuliaFormatter.jl](https://github.com/domluna/JuliaFormatter.jl) just like formatting script that 
+runs over the whole Trixi.jl directory. 
+You can copy the `pre-commit`-script into `.git/hooks/pre-commit` and it will check your formatting 
+before each commit. If errors are found the commit is aborted and you can add the corrections via
+```shell 
+git add -p
+```

utils/pre-commit

@@ -0,0 +1,40 @@
+#!/bin/sh
+
+# Copy this file into .git/hooks/pre-commit to execute before each commit. 
+# It checks and corrects the format for each file.
+# If incorrect formatting is found you can add the correction via git add -p
+
+echo "Checking format before committing"
+
+if git ref-parse --verify HEAD >/dev/null 2>&1
+then
+	against=HEAD
+else
+	# Initial commit: diff against an empty tree object
+        against=280fc57fade28e35046c3e884e587ffef05d3867
+fi
+
+# Redirect output to stderr.
+exec 1>&2
+
+# Create a list of files to format. 
+files=()
+
+for file in `git diff --cached --name-only`
+do
+	# only indent existing files, this is necessary since if we rename or delete
+	# a file it is added to the committed files and we thus would try to indent a	
+	# nonexisting file.
+	if [ ! -e $file ]
+	then
+		continue
+	fi
+	# We only indent .jl files
+ 	FILE_ENDING="${file##*.}"
+	if [ $FILE_ENDING = "jl" ]
+	then
+		files+=($file)
+	fi
+done
+
+julia utils/trixi-format-file.jl "${files[@]}"

utils/trixi-format-file.jl

@@ -0,0 +1,42 @@
+#!/usr/bin/env julia
+
+using Pkg
+Pkg.activate(; temp = true, io = devnull)
+Pkg.add("JuliaFormatter"; preserve = PRESERVE_ALL, io = devnull)
+
+using JuliaFormatter: format_file
+
+function main()
+    # Show help
+    if "-h" in ARGS || "--help" in ARGS
+        println("usage: trixi-format.jl PATH [PATH...]")
+        println()
+        println("positional arguments:")
+        println()
+        println("    PATH        One or more paths (directories or files) to format. Default: '.'")
+        return nothing
+    end
+
+    file_list = ARGS
+    if isempty(ARGS)
+        exit(0)
+    end
+    non_formatted_files = Vector{String}()
+    for file in file_list
+        println("Checking file " * file)
+        if !format_file(file)
+            push!(non_formatted_files, file)
+        end
+    end
+    if isempty(non_formatted_files)
+        exit(0)
+    else
+        @error "Some files have not been formatted! Formatting has been applied, run 'git add -p' to update changes."
+        for file in non_formatted_files
+            println(file)
+        end
+        exit(1)
+    end
+end
+
+main()