cli: fitconv add CSV to FIT File converter (#168)

* cli: fitconv add support for converting CSV file back into FIT file

* add copyright license

cmd/fitconv/Makefile

@@ -0,0 +1,31 @@
+.PHONY: build build-esc run pprof pprof-cpu pprof-mem trace took
+
+build:
+	go build main.go
+
+build-esc: # escape analysis
+	go build -gcflags="-m=2" main.go
+
+run:
+	make build
+	./main $(wordlist 2, $(words $(MAKECMDGOALS)),$(MAKECMDGOALS))
+
+pprof:
+	make build
+	./main -opt $(opt) $(wordlist 2, $(words $(MAKECMDGOALS)),$(MAKECMDGOALS))
+	go tool pprof -http=:8080 $(opt).pprof
+
+pprof-cpu:
+	make pprof opt=cpu $(wordlist 2, $(words $(MAKECMDGOALS)),$(MAKECMDGOALS))
+
+pprof-mem:
+	make pprof opt=mem $(wordlist 2, $(words $(MAKECMDGOALS)),$(MAKECMDGOALS))
+
+trace:
+	make build
+	./main -opt trace $(wordlist 2, $(words $(MAKECMDGOALS)),$(MAKECMDGOALS))
+	go tool trace trace.out
+
+took:
+	make build
+	./main -opt took $(wordlist 2, $(words $(MAKECMDGOALS)),$(MAKECMDGOALS))

cmd/fitconv/README.md

@@ -1,37 +1,39 @@
 # Fitconv
 
-Fitconv converts the FIT file into a CSV file, allowing us to read the FIT file in a human-readable format.
+Fitconv converts the FIT file into a CSV file, allowing us to read the FIT file in a human-readable format. And vice-versa, it converts CSV file back to FIT file allowing us editing FIT file in its CSV form using only code editor.
+
+This is designed to work seamlessly with CSVs produced by the Official FIT SDK's `FitCSVTool.jar`.
 
 Note:
 
-- Currently only FIT to CSV conversion is supported, other format might be added later when necessary (or requested).
+- Currently only `FIT to CSV` conversion and vice-versa (`CSV to FIT`) are supported, other format might be added later when necessary (or requested).
+- When converting `CSV to FIT`, unknown message and unknown fields are both skipped since we can't get the correct value's type since we don't have any context about it.
 
 ## Usage Examples
 
 ```sh
-go run main.go activity.fit activity2.fit
+go run main.go activity.fit activity2.csv
 
 # Output:
-# Converted! activity.csv
-# Converted! activity2.csv
+# 📄 "activity.fit" -> "activity.csv"
+# 🚀 "activity2.csv" -> "activity2.fit". [In total, 2 unknown messages are skipped]
 
 ls
 # activity.fit activity.csv activity2.fit activity2.csv
 ```
 
 ### Options
 
-| Options    | Description                                           |
-| ---------- | ----------------------------------------------------- |
-| -v         | Show version                                          |
-| -csv       | Convert FIT to CSV (default if not specified)         |
-| -disk      | Use disk instead of load everything in memory         |
-| -unknown   | Print 'unknown(68)' instead of 'unknown'              |
-| -valid     | Print only valid value and omit invalid value         |
-| -raw       | Use raw value instead of scaled value                 |
-| -deg       | Print GPS Positions in degress instead of semicircles |
-| -trim      | Trim trailing commas in every line (save storage)     |
-| -no-expand | [Decode Option] Do not expand components              |
+| Options    | Valid For       | Description                                            |
+| ---------- | --------------- | ------------------------------------------------------ |
+| -v         | All             | Show version                                           |
+| -disk      | FIT to CSV only | Use disk instead of load everything in memory          |
+| -unknown   | FIT to CSV only | Print 'unknown(68)' instead of 'unknown'               |
+| -valid     | FIT to CSV only | Print only valid value and omit invalid value          |
+| -raw       | FIT to CSV only | Use raw value instead of scaled value                  |
+| -deg       | FIT to CSV only | Print GPS Positions in degress instead of semicircles. |
+| -trim      | FIT to CSV only | Trim trailing commas in every line (save storage)      |
+| -no-expand | FIT to CSV only | [Decode Option] Do not expand components               |
 
 ```sh
 go run main.go -deg activity.fit activity2.fit