add man page

Justfile

@@ -9,6 +9,8 @@ gid := `id -g`
 date := `date -u --rfc-3339=seconds`
 cargo := `which cargo 2> /dev/null`
 
+default: build-docker build-release doc
+
 # main build
 build-release:
   cargo build --release
@@ -36,5 +38,12 @@ push-docker-latest: build-docker push-docker
   docker push forge.steck.dev/bryson/picca:latest
   docker image rm forge.steck.dev/bryson/picca:latest
 
+doc:
+  @mkdir -p target
+  sed s/\<VERSION\>/{{version}}/g man/picca.1.md | pandoc --standalone -t man > target/picca.1
+
+preview-man: doc
+  man target/picca.1
+
 clean:
   cargo clean

man/picca.1.md

@@ -0,0 +1,49 @@
+% PICCA(1) Version <VERSION> | User Commands
+% Written by Bryson Steck (bryson@steck.dev)
+% August 2025
+
+# NAME
+
+picca - a Parallel Implementation of Common Checksum Algorithms
+
+# SYNOPSIS
+
+picca [_OPTIONS_] [_FILE_]...
+
+# DESCRIPTION
+
+Print or verify checksums by reading files in parallel, using the SHA256 algorithm by default.
+
+When conditions are suitable, being able to hash multiple files in parallel can significantly increase performance with multi-file hashing operations. However, it can also significantly degrade performance depending on different factors with your particular system. Some factors to consider are:
+
+- The type of storage being used,
+- The type of processor(s) in the system,
+- The latency of I/O operations,
+- etc.
+
+# OPTIONS
+
+With no FILE(s) specified, or when FILE is a dash (-), picca will read from standard input.
+
+**-a, &ndash;&ndash;algorithm**=_ALGORITHM_
+: Specify the algorithm for hashing. The default value is sha256. A list of supported algorithms can be found in the **ALGORITHMS** section.
+
+**-c, &ndash;&ndash;check**=_CHECK_
+: Read checksums from the specified file and verify them. This argument can be specified multiple times to read checksums from multiple files.
+
+**-d, &ndash;&ndash;debug**
+: Enable debug output for troubleshooting purposes. Messages output to standard error.
+
+**-f, &ndash;&ndash;canonicalize**
+: Show canonicalized file paths; convert relative paths to absolute paths.
+
+**-h, &ndash;&ndash;help**
+: Show command usage and available options
+
+**-t, &ndash;&ndash;threads**=_THREADS_
+: Use at most, at any given time, this number of threads. By default, picca will detect the amount of processors on the system and use that as the thread count. Using 0 for this value results in the default behavior; this is the same as omitting this option.
+
+The following option is only useful when verifying checksums with the **-c** flag:
+
+**-q, &ndash;&ndash;quiet**
+: Only print checksums that fail verification; do not print anything to standard output if a verfication is successful. Helpful to limit the amount of information printed to the screen.