Create basic-git.nu (#687)

It's a really simple and naive git status implementation for the prompt
in nushell. Tested on the latest version of nushell.

modules/prompt/basic-git.nu

@@ -0,0 +1,68 @@
+# Max Brown
+# a very basic git prompt
+# sort of like panache-git, but fewer than 60 lines of code.
+
+# use as below without the comments and in your
+# env.nu file
+
+
+#  use path/to/basic-git.nu basic-git-left-prompt
+
+#  $env.PROMPT_COMMAND = {||
+#		 let left = create_left_prompt
+#		 basic-git-left-prompt $left
+# }
+
+def in_git_repo [] {
+  (do --ignore-errors { git rev-parse --abbrev-ref HEAD } | is-empty) == false
+}
+
+export def basic-git-left-prompt [in_left_prompt] {
+
+  # if we're in a repo, let's go!
+  let currently_in_git_repo = in_git_repo
+
+  if $currently_in_git_repo {
+    # get the branch info first
+    let branch_info = git branch -l
+      | lines
+      | filter {|e| $e | str contains "*" }
+      | each {|e| $e | str replace "* " "="}
+      | get 0
+    let git_status = git status -s
+
+    # get the status in short
+    let git_status = $git_status
+      | lines
+      | str replace -r '(.* ).*' '$1'
+      | sort
+      | uniq -c
+      | insert type {
+        |e| if ($e.value | str contains "M") {
+            "blue"
+          } else if ($e.value | str contains "??") {
+            "yellow_bold"
+          } else if ($e.value | str contains "D") {
+            "red_bold"
+          } else ""
+        }
+      | each {
+          |e| $"(ansi $e.type)($e.count)($e.value | str trim)(ansi reset)"
+        }
+      | reduce --fold '' {|str all| $"($all),($str)" }
+      | str substring 1..
+
+    let final_git_status = if $git_status == "" {
+      ""
+    } else {
+      $" ($git_status)"
+    }
+
+    # construct the prompt
+    $"($in_left_prompt)(ansi reset) [($branch_info)($final_git_status)]"
+
+  } else {
+    # otherwise just return the normal prompt
+    $in_left_prompt
+  }
+}