Don't set safe.dir=* in main app

Dockerfile.in

@@ -103,7 +103,6 @@ RUN rm -rf \
     /usr/lib/git-core/git-http-push \
     /usr/lib/git-core/git-imap-send \
     /usr/lib/git-core/git-instaweb \
-    /usr/lib/git-core/git-sh-i18n--envsubst \
     /usr/lib/git-core/scalar \
     /usr/lib/openssh/ssh-keysign \
     /usr/lib/openssh/ssh-pkcs11-helper \

README.md

@@ -312,7 +312,28 @@ OPTIONS
     --git-config <string>, $GITSYNC_GIT_CONFIG
             Additional git config options in a comma-separated 'key:val'
             format.  The parsed keys and values are passed to 'git config' and
-            must be valid syntax for that command.
+            must be valid syntax for that command.  This is similar to
+            --git-config-add, but uses a single comma-separated string.
+
+            Both keys and values can be either quoted or unquoted strings.
+            Within quoted keys and all values (quoted or not), the following
+            escape sequences are supported:
+                '\n' => [newline]
+                '\t' => [tab]
+                '\"' => '"'
+                '\,' => ','
+                '\\' => '\'
+            To include a colon within a key (e.g. a URL) the key must be
+            quoted.  Within unquoted values commas must be escaped.  Within
+            quoted values commas may be escaped, but are not required to be.
+            Any other escape sequence is an error.
+
+    --git-config-add <string>
+            Add one git config option.  The parsed key and value are passed to
+            'git config' and must be valid syntax for that command.  This flag
+            can be specified more than once.  This is similar to --git-config,
+            but allows multiple discrete uses of the flag instead of a single
+            comma-separated string.
 
             Both keys and values can be either quoted or unquoted strings.
             Within quoted keys and all values (quoted or not), the following