Index: src/blob.c
==================================================================
--- src/blob.c
+++ src/blob.c
@@ -792,11 +792,11 @@
     }
     nName = file_simplify_name(zName, nName, 0);
     for(i=1; i<nName; i++){
       if( zName[i]=='/' ){
         zName[i] = 0;
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__CYGWIN__)
         /*
         ** On Windows, local path looks like: C:/develop/project/file.txt
         ** The if stops us from trying to create a directory of a drive letter
         ** C: in this example.
         */
@@ -804,11 +804,11 @@
 #endif
           if( file_mkdir(zName, 1) && file_isdir(zName)!=1 ){
             fossil_fatal_recursive("unable to create directory %s", zName);
             return 0;
           }
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__CYGWIN__)
         }
 #endif
         zName[i] = '/';
       }
     }
@@ -1104,11 +1104,11 @@
     zUtf8 = blob_str(pBlob) + bomSize;
     blob_zero(&temp);
     blob_append(&temp, zUtf8, -1);
     blob_swap(pBlob, &temp);
     blob_reset(&temp);
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__CYGWIN__)
   }else if( starts_with_utf16_bom(pBlob, &bomSize, &bomReverse) ){
     zUtf8 = blob_buffer(pBlob);
     if( bomReverse ){
       /* Found BOM, but with reversed bytes */
       unsigned int i = blob_size(pBlob);
@@ -1124,13 +1124,15 @@
     zUtf8 = blob_str(pBlob) + bomSize;
     zUtf8 = fossil_unicode_to_utf8(zUtf8);
     blob_zero(pBlob);
     blob_append(pBlob, zUtf8, -1);
     fossil_unicode_free(zUtf8);
+#endif /* _WIN32 ||  __CYGWIN__ */
+#if defined(_WIN32)
   }else if( useMbcs ){
     zUtf8 = fossil_mbcs_to_utf8(blob_str(pBlob));
     blob_reset(pBlob);
     blob_append(pBlob, zUtf8, -1);
     fossil_mbcs_free(zUtf8);
 #endif /* _WIN32 */
   }
 }

Index: src/checkin.c
==================================================================
--- src/checkin.c
+++ src/checkin.c
@@ -966,11 +966,11 @@
       if ( encodingOk ){
         return 0; /* We don't want encoding warnings for this file. */
       }
       zWarning = "Unicode";
       zDisable = "\"encoding-glob\" setting";
-#ifndef _WIN32
+#if !defined(_WIN32) && !defined(__CYGWIN__)
       zConvert = ""; /* On Unix, we cannot easily convert Unicode files. */
 #endif
     }
     file_relative_name(zFilename, &fname, 0);
     blob_zero(&ans);

Index: src/utf8.c
==================================================================
--- src/utf8.c
+++ src/utf8.c
@@ -23,10 +23,18 @@
 #include "utf8.h"
 #include <sqlite3.h>
 #ifdef _WIN32
 # include <windows.h>
 #endif
+#ifdef __CYGWIN__
+# include <sys/cygwin.h>
+# define CP_UTF8 65001
+  __declspec(dllimport) extern __stdcall int WideCharToMultiByte(int, int,
+      const char *, int, const char *, int, const char *, const char *);
+  __declspec(dllimport) extern __stdcall int MultiByteToWideChar(int, int,
+      const char *, int, wchar_t*, int);
+#endif
 
 #ifdef _WIN32
 /*
 ** Translate MBCS to UTF-8.  Return a pointer to the translated text.
 ** Call fossil_mbcs_free() to deallocate any memory used to store the
@@ -42,19 +50,20 @@
 ** any memory used to hold the translation
 */
 void fossil_mbcs_free(char *zOld){
   sqlite3_free(zOld);
 }
+#endif /* _WIN32 */
 
 /*
 ** Translate Unicode text into UTF-8.
 ** Return a pointer to the translated text.
 ** Call fossil_unicode_free() to deallocate any memory used to store the
 ** returned pointer when done.
 */
 char *fossil_unicode_to_utf8(const void *zUnicode){
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__CYGWIN__)
   int nByte = WideCharToMultiByte(CP_UTF8, 0, zUnicode, -1, 0, 0, 0, 0);
   char *zUtf = sqlite3_malloc( nByte );
   if( zUtf==0 ){
     return 0;
   }
@@ -69,11 +78,11 @@
 ** Translate UTF-8 to unicode for use in system calls.  Return a pointer to the
 ** translated text..  Call fossil_unicode_free() to deallocate any memory
 ** used to store the returned pointer when done.
 */
 void *fossil_utf8_to_unicode(const char *zUtf8){
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__CYGWIN__)
   int nByte = MultiByteToWideChar(CP_UTF8, 0, zUtf8, -1, 0, 0);
   wchar_t *zUnicode = sqlite3_malloc( nByte * 2 );
   if( zUnicode==0 ){
     return 0;
   }
@@ -87,17 +96,16 @@
 /*
 ** Deallocate any memory that was previously allocated by
 ** fossil_unicode_to_utf8().
 */
 void fossil_unicode_free(void *pOld){
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__CYGWIN__)
   sqlite3_free(pOld);
 #else
   fossil_free(pOld);
 #endif
 }
-#endif /* _WIN32 */
 
 #if defined(__APPLE__) && !defined(WITHOUT_ICONV)
 # include <iconv.h>
 #endif
 
@@ -160,17 +168,17 @@
 ** Call fossil_filename_free() to deallocate any memory used to store the
 ** returned pointer when done.
 */
 void *fossil_utf8_to_filename(const char *zUtf8){
 #ifdef _WIN32
-  int nByte = MultiByteToWideChar(CP_UTF8, 0, zUtf8, -1, 0, 0);
-  wchar_t *zUnicode = sqlite3_malloc( nByte * 2 );
+  int nChar = MultiByteToWideChar(CP_UTF8, 0, zUtf8, -1, 0, 0);
+  wchar_t *zUnicode = sqlite3_malloc( nChar * 2 );
   wchar_t *wUnicode = zUnicode;
   if( zUnicode==0 ){
     return 0;
   }
-  MultiByteToWideChar(CP_UTF8, 0, zUtf8, -1, zUnicode, nByte);
+  MultiByteToWideChar(CP_UTF8, 0, zUtf8, -1, zUnicode, nChar);
   while( *wUnicode != '\0' ){
     if( *wUnicode == '/' ){
       *wUnicode = '\\';
     }
     ++wUnicode;
@@ -178,22 +186,31 @@
   return zUnicode;
 #elif defined(__CYGWIN__)
   char *zPath, *p;
   if( fossil_isalpha(zUtf8[0]) && (zUtf8[1]==':')
       && (zUtf8[2]=='\\' || zUtf8[2]=='/')) {
-    int n = strlen(zUtf8);
-    zPath = fossil_malloc( n+10 );
-    memcpy(zPath, "/cygdrive/", 10);
-    zPath[10] = zUtf8[0];
-    memcpy(zPath+11, zUtf8+2, n-1);
+    /* win32 absolute path starting with drive specifier. */
+    int nByte;
+    wchar_t zUnicode[2000];
+    wchar_t *wUnicode = zUnicode;
+    MultiByteToWideChar(CP_UTF8, 0, zUtf8, -1, zUnicode, count(zUnicode));
+    while( *wUnicode != '\0' ){
+      if( *wUnicode == '/' ){
+        *wUnicode = '\\';
+      }
+      ++wUnicode;
+    }
+    nByte = cygwin_conv_path(CCP_WIN_W_TO_POSIX, zUnicode, NULL, 0);
+    zPath = fossil_malloc(nByte);
+    cygwin_conv_path(CCP_WIN_W_TO_POSIX, zUnicode, zPath, nByte);
   } else {
     zPath = fossil_strdup(zUtf8);
-  }
-  zUtf8 = p = zPath;
-  while( (*p = *zUtf8++) != 0){
-    if (*p++ == '\\' ) {
-      p[-1] = '/';
+    zUtf8 = p = zPath;
+    while( (*p = *zUtf8++) != 0){
+      if (*p++ == '\\' ) {
+        p[-1] = '/';
+      }
     }
   }
   return zPath;
 #elif defined(__APPLE__) && !defined(WITHOUT_ICONV)
   return fossil_strdup(zUtf8);