Add -e flag to explain what the previous smiley face means. This

requires us to also know what the previous return signal is, so
if XD is given a return code, it passes it through when finishing
execution.

XD.c

@@ -1,7 +1,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#ifdef ERR
+#include <ctype.h>
+
+#if defined(ERR) || defined(EXPLAIN)
 #include <stdarg.h>
 #endif
 
@@ -13,7 +15,7 @@
 
 #define P(X) fwrite(X, 1, 1, stdout)
 
-#ifdef ERR
+#if defined(ERR) || defined(EXPLAIN)
 void
 l(const char *fmt, ...)
 {
@@ -30,11 +32,23 @@ l(const char *fmt, ...)
     fputc('\n', stderr);
   }
 }
+#endif
+
+#ifdef ERR
 #define L(...) l(__VA_ARGS__)
 #else
 #define L(...)
 #endif
 
+#ifdef EXPLAIN
+static int explain = 0;
+#define E(...) if (explain) {    \
+                 l(__VA_ARGS__); \
+               } else
+#else
+#define E(...)
+#endif
+
 #ifdef GIT
 /**
  * @brief search all parent directories for a git repo
@@ -225,6 +239,10 @@ main(int argc, char *argv[])
   if (argc > 1 && strcmp(argv[1], "-v") == 0) {
     printf("XD [number] v%s\n", VERSION);
     return 0;
+  #ifdef EXPLAIN
+  } else if (argc > 1 && strcmp(argv[1], "-e") == 0) {
+    explain = 1;
+  #endif
   }
 
   #ifdef GIT
@@ -233,19 +251,25 @@ main(int argc, char *argv[])
   if ((repo = init_git())) {
     /* change the eyes depending on the current git repo's status */
     if (has_stashes(repo)) {
+      E("The current git repo has stashed changes.")
       P("8"); /* goggle eyes if we have some stashed changes */
     } else if (git_repository_is_empty(repo)) {
+      E("This is a new git repo.")
       P("B"); /* sunglasses if we're in a new repo with no HEAD */
     } else {
+      E("In a git repository.")
       P(";"); /* wink when we're in a git repo */
     }
 
     /* change the nose depending on the current git repo's status */
     if (has_staged(repo)) {
+      E("The're staged changes.")
       P("*"); /* change to broken nose for staged changes */
     } else if (has_untracked(repo)) {
+      E("There are untracked changes in the repository.")
       P("^"); /* add a little nose when there are untracked changes in the repo */
     } else if (git_repository_head_detached(repo)) {
+      E("The HEAD is detached.")
       P("-"); /* add a minus nose when the HEAD is detached */
     }
     git_repository_free(repo);
@@ -253,6 +277,7 @@ main(int argc, char *argv[])
   } else
   #endif
   if (1) {
+    E("Not in a git repository.")
     P(":");
   }
 
@@ -264,13 +289,31 @@ main(int argc, char *argv[])
   /* change mouth based on exit code */
   if (code >= 0) {
     switch (code) {
-      case 0: P(")"); break; /* all good */
-      case 130: P("O"); break; /* Ctrl-c pressed (SIGTERM) */
-      case 126: P("P"); break; /* permission denied */
-      case 127: P("/"); break; /* command not found */
-      default: P("("); break; /* all other codes (usually the program saying it has failed) */
+      case 0: /* all good */
+        E("Return code of %d, no errors.", code)
+        P(")");
+        break;
+      case 130: /* Ctrl-c pressed (SIGTERM) */
+        E("Return code of %d, ctrl-c was pressed, or SIGTERM sent.", code)
+        P("O");
+        break;
+      case 126: /* permission denied */
+        E("Return code of %d, permission denied.", code)
+        P("P");
+        break;
+      case 127: /* command not found */
+        E("Return code of %d, command not found.", code)
+        P("/");
+        break;
+      default: /* all other codes (usually the program saying it has failed) */
+        E("Return code of %d, probably an error with the program.", code)
+        P("(");
+        break;
     }
   } else {
+    E("No code information passed in.")
     P("|"); /* no code info */
   }
+
+  return code;
 }