Migrate fish_history from config to data dir

New implementation of migration code within the history_t class will
copy the contents of the old fish_history found in the config directory
to its new location in the data directory.  The old file is left intact.

This is done only in the event that a fish_history is not already found in
the data directory ($XDG_DATA_HOME/fish or ~/.local/share/fish).

src/history.cpp

@@ -1664,6 +1664,53 @@ bool history_t::is_empty(void)
     return empty;
 }
 
+
+/* Populates from older location (in config path, rather than data path)
+   This is accomplished by clearing ourselves, and copying the contents of
+   the old history file to the new history file.  The new contents will
+   automatically be re-mapped later.
+*/
+void history_t::populate_from_config_path()
+{
+    wcstring old_file;
+    if (path_get_config(old_file)) {
+        old_file.append(L"/");
+        old_file.append(name);
+        old_file.append(L"_history");
+        int src_fd = wopen_cloexec(old_file, O_RDONLY, 0);
+        if (src_fd != -1)
+        {
+            wcstring new_file;
+            history_filename(new_file, L"");
+
+            /* clear must come after we've retrieved the new_file name,
+               and before we open destination file descriptor,
+               since it destroys the name and the file */
+            this->clear();
+
+            int dst_fd = wopen_cloexec(new_file, O_WRONLY | O_CREAT, 0644);
+
+            char buf[BUFSIZ];
+            size_t size;
+            while ((size = read(src_fd, buf, BUFSIZ)) > 0) {
+                ssize_t written = write(dst_fd, buf, size);
+                if (written == -1) {
+                    /*
+                      This message does not have high enough priority to
+                      be shown by default.
+                    */
+                    debug(2, L"Error when writing history file");
+                    break;
+                }
+            }
+
+            close(src_fd);
+            close(dst_fd);
+        }
+    }
+}
+
+
 /* Indicate whether we ought to import the bash history file into fish */
 static bool should_import_bash_history_line(const std::string &line)
 {

src/history.h

@@ -64,7 +64,7 @@ private:
 
     /** Paths that we require to be valid for this item to be autosuggested */
     path_list_t required_paths;
-    
+
 public:
     const wcstring &str() const
     {
@@ -141,7 +141,7 @@ private:
 
     /** Whether we have a pending item. If so, the most recently added item is ignored by item_at_index. */
     bool has_pending_item;
-    
+
     /** Whether we should disable saving to the file for a time */
     uint32_t disable_automatic_save_counter;
 
@@ -222,7 +222,7 @@ public:
 
     /** Add a new pending history item to the end, and then begin file detection on the items to determine which arguments are paths */
     void add_pending_with_file_detection(const wcstring &str);
-    
+
     /** Resolves any pending history items, so that they may be returned in history searches. */
     void resolve_pending();
 
@@ -236,6 +236,9 @@ public:
     /** Irreversibly clears history */
     void clear();
 
+    /** Populates from older location ()in config path, rather than data path) */
+    void populate_from_config_path();
+
     /** Populates from a bash history file */
     void populate_from_bash(FILE *f);
 

src/reader.cpp

@@ -1226,7 +1226,7 @@ static bool insert_string(editable_line_t *el, const wcstring &str, bool allow_e
     size_t len = str.size();
     if (len == 0)
         return false;
-    
+
     /* Start inserting. If we are expanding abbreviations, we have to do this after every space (see #1434), so look for spaces. We try to do this efficiently (rather than the simpler character at a time) to avoid expensive work in command_line_changed() */
     size_t cursor = 0;
     while (cursor < len)
@@ -1236,14 +1236,14 @@ static bool insert_string(editable_line_t *el, const wcstring &str, bool allow_e
         size_t char_triggering_expansion_pos = allow_expand_abbreviations ? str.find_first_of(expansion_triggering_chars, cursor) : wcstring::npos;
         bool has_expansion_triggering_char = (char_triggering_expansion_pos != wcstring::npos);
         size_t range_end = (has_expansion_triggering_char ? char_triggering_expansion_pos + 1 : len);
-        
+
         /* Insert from the cursor up to but not including the range end */
         assert(range_end > cursor);
         el->insert_string(str, cursor, range_end - cursor);
-        
+
         update_buff_pos(el, el->position);
         data->command_line_changed(el);
-        
+
         /* If we got an expansion trigger, then the last character we inserted was it (i.e. was a space). Expand abbreviations. */
         if (has_expansion_triggering_char && allow_expand_abbreviations)
         {
@@ -1253,16 +1253,16 @@ static bool insert_string(editable_line_t *el, const wcstring &str, bool allow_e
         }
         cursor = range_end;
     }
-    
+
     if (el == &data->command_line)
     {
         data->suppress_autosuggestion = false;
-        
+
         /* Syntax highlight. Note we must have that buff_pos > 0 because we just added something nonzero to its length  */
         assert(el->position > 0);
         reader_super_highlight_me_plenty(-1);
     }
-    
+
     reader_repaint();
 
     return true;
@@ -1562,7 +1562,7 @@ static void accept_autosuggestion(bool full)
     {
         /* Accepting an autosuggestion clears the pager */
         clear_pager();
-        
+
         /* Accept the autosuggestion */
         if (full)
         {
@@ -1877,7 +1877,7 @@ static bool handle_completions(const std::vector<completion_t> &comp, bool conti
                     break;
             }
         }
-        
+
         /* Determine if we use the prefix. We use it if it's non-empty and it will actually make the command line longer. It may make the command line longer by virtue of not using REPLACE_TOKEN (so it always appends to the command line), or by virtue of replacing the token but being longer than it. */
         bool use_prefix = common_prefix.size() > (will_replace_token ? tok.size() : 0);
         assert(! use_prefix || ! common_prefix.empty());
@@ -2660,7 +2660,13 @@ void reader_set_exit_on_interrupt(bool i)
 
 void reader_import_history_if_necessary(void)
 {
-    /* Import history from bash, etc. if our current history is empty */
+    /* Import history from older location (config path) if our current history is empty */
+    if (data->history && data->history->is_empty())
+    {
+        data->history->populate_from_config_path();
+    }
+
+    /* Import history from bash, etc. if our current history is still empty */
     if (data->history && data->history->is_empty())
     {
         /* Try opening a bash file. We make an effort to respect $HISTFILE; this isn't very complete (AFAIK it doesn't have to be exported), and to really get this right we ought to ask bash itself. But this is better than nothing.
@@ -3157,7 +3163,7 @@ const wchar_t *reader_readline(int nchars)
 
                     editable_line_t *el = data->active_edit_line();
                     insert_string(el, arr, true);
-                    
+
                     /* End paging upon inserting into the normal command line */
                     if (el == &data->command_line)
                     {
@@ -3440,7 +3446,7 @@ const wchar_t *reader_readline(int nchars)
                 {
                     begin--;
                 }
-                
+
                 /* Push end forwards to just past the next newline, or just past the last char. */
                 size_t end = el->position;
                 while (buff[end] != L'\0')