fix: use iconv for non-utf-8 encodings

Neovim appears to be built with iconv. We can access this to convert
non-utf-8 command outputs (e.g. from 'git show <file>').

Fixes #522

lua/gitsigns.lua

@@ -241,7 +241,7 @@ local attach0 = function(cbuf, aucmd)
       return
    end
 
-   local git_obj = git.Obj.new(file)
+   local git_obj = git.Obj.new(file, vim.bo[cbuf].fileencoding)
    if not git_obj then
       dprint('Empty git obj')
       return

lua/gitsigns/git.lua

@@ -108,6 +108,7 @@ local M = {BlameInfo = {}, Version = {}, Repo = {}, FileProps = {}, Obj = {}, }
 
 
 
+
 
 
 local in_git_dir = function(file)
@@ -392,6 +393,13 @@ Obj.get_show_text = function(self, revision)
       end
    end
 
+   if self.encoding ~= 'utf-8' then
+      scheduler()
+      for i, l in ipairs(stdout) do
+         stdout[i] = vim.fn.iconv(l, self.encoding, 'utf-8')
+      end
+   end
+
    return stdout, stderr
 end
 
@@ -508,7 +516,7 @@ Obj.has_moved = function(self)
    end
 end
 
-Obj.new = function(file)
+Obj.new = function(file, encoding)
    if in_git_dir(file) then
       dprint('In git dir')
       return nil
@@ -516,6 +524,7 @@ Obj.new = function(file)
    local self = setmetatable({}, { __index = Obj })
 
    self.file = file
+   self.encoding = encoding
    self.repo = Repo.new(util.dirname(file))
 
    if not self.repo.gitdir then

teal/ffi.d.tl

@@ -11,11 +11,15 @@ end
 
 local record ffi
   cdef: function(string)
-  new: function(string, ...:any)
+  load: function(string): any
+  new: function(string, ...:any): any
   string: function(any, number): string
-  gc: function(any, any): any
+  gc: function<T>(T, function): T
   C: Cdefs
-  cast: function(string, function): CCB
+  cast: function(string, any): CCB
+  errno: function(): integer
+  copy: function
+  metatype: function(string, any)
 end
 
 return ffi

teal/gitsigns.tl

@@ -241,7 +241,7 @@ local attach0 = function(cbuf: integer, aucmd: string)
     return
   end
 
-  local git_obj = git.Obj.new(file)
+  local git_obj = git.Obj.new(file, vim.bo[cbuf].fileencoding)
   if not git_obj then
     dprint('Empty git obj')
     return

teal/gitsigns/git.tl

@@ -94,6 +94,7 @@ local record M
     has_conflicts : boolean
     i_crlf        : boolean  -- Object has crlf
     w_crlf        : boolean  -- Working copy has crlf
+    encoding      : string
 
     command              : function(Obj, {string}, GJobSpec): {string}, string
     update_file_info     : function(Obj, boolean): boolean
@@ -105,7 +106,7 @@ local record M
     stage_hunks          : function(Obj, {Hunk}, boolean)
     stage_lines          : function(Obj, {string})
     has_moved            : function(Obj): string
-    new                  : function(string): Obj
+    new                  : function(string, string): Obj
   end
 
 end
@@ -392,6 +393,13 @@ Obj.get_show_text = function(self: Obj, revision: string): {string}, string
     end
   end
 
+  if self.encoding ~= 'utf-8' then
+    scheduler()
+    for i, l in ipairs(stdout) do
+      stdout[i] = vim.fn.iconv(l, self.encoding, 'utf-8')
+    end
+  end
+
   return stdout, stderr
 end
 
@@ -508,7 +516,7 @@ Obj.has_moved = function(self: Obj): string
   end
 end
 
-Obj.new = function(file: string): Obj
+Obj.new = function(file: string, encoding: string): Obj
   if in_git_dir(file) then
       dprint('In git dir')
       return nil
@@ -516,6 +524,7 @@ Obj.new = function(file: string): Obj
   local self = setmetatable({} as Obj, {__index = Obj})
 
   self.file = file
+  self.encoding = encoding
   self.repo = Repo.new(util.dirname(file))
 
   if not self.repo.gitdir then

types/types.d.tl

@@ -216,6 +216,7 @@ end
 global record vim
   api: api
   record fn
+    iconv: function(string, string, string): string
     line: function(string): integer
     join: function({any}, string): string
     getpos: function(string): {integer}
@@ -307,6 +308,7 @@ global record vim
   record BufOption
     {BufOption}
     fileformat: string
+    fileencoding: string
     filetype: string
     modifiable: boolean
     modified: boolean