Add git-commit-plot example

Author: kojix2

examples/git-commit-plot.cr

@@ -0,0 +1,57 @@
+require "../src/unicode_plot"
+
+include UnicodePlot
+
+# Build as a Git plugin:
+#   crystal build examples/time_axis.cr -o git-commit-plot
+#   mv git-commit-plot ~/.local/bin/
+# Then run:
+#   git commit-plot
+#   git commit-plot /path/to/repo
+
+directory = File.expand_path(ARGV[0]? || Dir.current)
+_, terminal_width = UnicodePlot.out_stream_size(STDOUT)
+plot_width = Math.max(20, terminal_width - 32)
+
+def date_from_git(value : String) : Time
+  year, month, day = value.split("-").map(&.to_i)
+  Time.utc(year, month, day)
+end
+
+stdout = IO::Memory.new
+stderr = IO::Memory.new
+status = Process.run(
+  "git",
+  ["-C", directory, "log", "--date=short", "--format=%ad"],
+  output: stdout,
+  error: stderr
+)
+
+unless status.success?
+  abort "git log failed in #{directory}: #{stderr.to_s.strip}"
+end
+
+counts = Hash(Time, Int32).new(0)
+stdout.to_s.each_line do |line|
+  next if line.empty?
+  counts[date_from_git(line)] += 1
+end
+
+abort "no commits found in #{directory}" if counts.empty?
+
+dates = counts.keys.sort!
+values = dates.map { |date| counts[date].to_f64 }
+
+plot = stairs(
+  dates,
+  values,
+  format: "%F",
+  title: "Git commits per day",
+  xlabel: "commit date",
+  ylabel: "commits",
+  name: "commits",
+  color: :green,
+  width: plot_width
+)
+
+puts plot