build: don't require glib 2.58 for g_canonicalize_file

GLib version is probably still a bit too new, so simply lift the
function needed.

Fixes: #1712.

configure.ac

@@ -138,7 +138,7 @@ AS_IF([test -z "$PKG_CONFIG"],
 )
 
 # glib2?
-PKG_CHECK_MODULES(GLIB,glib-2.0 >= 2.38 gobject-2.0 gio-2.0)
+PKG_CHECK_MODULES(GLIB,glib-2.0 >= 2.50 gobject-2.0 gio-2.0)
 glib_version="$($PKG_CONFIG --modversion glib-2.0)"
 
 # gmime, version 3.0 or higher

lib/mu-msg-file.c

@@ -110,7 +110,7 @@ init_file_metadata (MuMsgFile *self, const char* path, const gchar* mdir,
 
 	self->_timestamp = statbuf.st_mtime;
 	self->_size	 = (size_t)statbuf.st_size;
-	self->_path      = g_canonicalize_filename(path, NULL);
+	self->_path      = mu_canonicalize_filename(path, NULL);
 	self->_maildir   = g_strdup(mdir ? mdir : "");
 
 	return TRUE;

lib/utils/mu-util.c

@@ -501,3 +501,141 @@ mu_util_read_password (const char *prompt)
 
 	return g_strdup (pass);
 }
+
+
+/* Pick g_canonicalize_file name from glib >= 2.58 */
+
+/**
+ * g_canonicalize_filename:
+ * @filename: (type filename): the name of the file
+ * @relative_to: (type filename) (nullable): the relative directory, or %NULL
+ * to use the current working directory
+ *
+ * Gets the canonical file name from @filename. All triple slashes are turned into
+ * single slashes, and all `..` and `.`s resolved against @relative_to.
+ *
+ * Symlinks are not followed, and the returned path is guaranteed to be absolute.
+ *
+ * If @filename is an absolute path, @relative_to is ignored. Otherwise,
+ * @relative_to will be prepended to @filename to make it absolute. @relative_to
+ * must be an absolute path, or %NULL. If @relative_to is %NULL, it'll fallback
+ * to g_get_current_dir().
+ *
+ * This function never fails, and will canonicalize file paths even if they don't
+ * exist.
+ *
+ * No file system I/O is done.
+ *
+ * Returns: (type filename) (transfer full): a newly allocated string with the
+ * canonical file path
+ * Since: 2.58
+ */
+gchar *
+mu_canonicalize_filename (const gchar *filename,
+                         const gchar *relative_to)
+{
+  gchar *canon, *start, *p, *q;
+  guint i;
+
+  g_return_val_if_fail (relative_to == NULL || g_path_is_absolute (relative_to), NULL);
+
+  if (!g_path_is_absolute (filename))
+    {
+      gchar *cwd_allocated = NULL;
+      const gchar  *cwd;
+
+      if (relative_to != NULL)
+        cwd = relative_to;
+      else
+        cwd = cwd_allocated = g_get_current_dir ();
+
+      canon = g_build_filename (cwd, filename, NULL);
+      g_free (cwd_allocated);
+    }
+  else
+    {
+      canon = g_strdup (filename);
+    }
+
+  start = (char *)g_path_skip_root (canon);
+
+  if (start == NULL)
+    {
+      /* This shouldn't really happen, as g_get_current_dir() should
+         return an absolute pathname, but bug 573843 shows this is
+         not always happening */
+      g_free (canon);
+      return g_build_filename (G_DIR_SEPARATOR_S, filename, NULL);
+    }
+
+  /* POSIX allows double slashes at the start to
+   * mean something special (as does windows too).
+   * So, "//" != "/", but more than two slashes
+   * is treated as "/".
+   */
+  i = 0;
+  for (p = start - 1;
+       (p >= canon) &&
+         G_IS_DIR_SEPARATOR (*p);
+       p--)
+    i++;
+  if (i > 2)
+    {
+      i -= 1;
+      start -= i;
+      memmove (start, start+i, strlen (start+i) + 1);
+    }
+
+  /* Make sure we're using the canonical dir separator */
+  p++;
+  while (p < start && G_IS_DIR_SEPARATOR (*p))
+    *p++ = G_DIR_SEPARATOR;
+
+  p = start;
+  while (*p != 0)
+    {
+      if (p[0] == '.' && (p[1] == 0 || G_IS_DIR_SEPARATOR (p[1])))
+        {
+          memmove (p, p+1, strlen (p+1)+1);
+        }
+      else if (p[0] == '.' && p[1] == '.' && (p[2] == 0 || G_IS_DIR_SEPARATOR (p[2])))
+        {
+          q = p + 2;
+          /* Skip previous separator */
+          p = p - 2;
+          if (p < start)
+            p = start;
+          while (p > start && !G_IS_DIR_SEPARATOR (*p))
+            p--;
+          if (G_IS_DIR_SEPARATOR (*p))
+            *p++ = G_DIR_SEPARATOR;
+          memmove (p, q, strlen (q)+1);
+        }
+      else
+        {
+          /* Skip until next separator */
+          while (*p != 0 && !G_IS_DIR_SEPARATOR (*p))
+            p++;
+
+          if (*p != 0)
+            {
+              /* Canonicalize one separator */
+              *p++ = G_DIR_SEPARATOR;
+            }
+        }
+
+      /* Remove additional separators */
+      q = p;
+      while (*q && G_IS_DIR_SEPARATOR (*q))
+        q++;
+
+      if (p != q)
+        memmove (p, q, strlen (q) + 1);
+    }
+
+  /* Remove trailing slashes */
+  if (p > start && G_IS_DIR_SEPARATOR (*(p-1)))
+    *(p-1) = 0;
+
+  return canon;
+}

lib/utils/mu-util.h

@@ -49,6 +49,20 @@ G_BEGIN_DECLS
 char* mu_util_dir_expand (const char* path)
 	G_GNUC_MALLOC G_GNUC_WARN_UNUSED_RESULT;
 
+
+/**
+ * See g_canonicalize_filename
+ *
+ * @param filename
+ * @param relative_to
+ *
+ * @return
+ */
+char *mu_canonicalize_filename (const gchar *filename,
+                                const gchar *relative_to)
+        G_GNUC_MALLOC G_GNUC_WARN_UNUSED_RESULT;
+
+
 /**
  * guess the maildir; first try $MAILDIR; if it is unset or
  * non-existent, try ~/Maildir if both fail, return NULL