update README to reflect new placeholder model

README.md

@@ -9,14 +9,14 @@ xlsx-git provides hooks to convert .xlsx files into their XML format before comm
 ## Issues
  - **NOT TESTED AND MAY WIPE OUT ALL YOUR FILES**.
  - risk of conflicts with other files
- - xlsx files don't actually appear in the repository
+
+### Checkout restrictions
+When you have .xlsx files in your repo, you won't be able to checkout other branches or commits because the post-checkout hook always leaves the .xlsx files in a "modified" state. This protects you against accidentally losing saved but not committed work in Excel. Before `checkout`, use `git stash` to get to a clean state by hiding away your Excel files.
 
 ## Installation and Use
 1. Place pre-commit and post-commit in the .git/hooks/ directory of your repository. 
 2. Make sure they are executable (e.g., `chmod 755 *-commit`)
 
 ## Dependencies
-I use Cygwin and the GNU tools that go with that. With Git Extensions or MinGW you may need some other basic commands, like dirname and basename. Some packages in particular:
-* `bash` >= 4.0
-* `xmllint`
+I use Cygwin and the GNU tools that go with that. With Git Extensions or MinGW you may need some other basic commands, like dirname and basename. In addition:
 * `zip` and `unzip`

post-checkout

@@ -4,6 +4,7 @@
 #                      the XML in the repository, not the zip file. 
 #
 #                      companion to pre-commit-excel
+#                      currently identical to post-commit
 
 # -- config -- #
 TMP_PREFIX='.~' # prefix XML directory--should NOT conflict with 
@@ -16,6 +17,7 @@ echo "=== Post-checkout XLSX processing ===="
 
 repack_xlsx () {
     # re-zip the XML directory 
+    rm "$1"
     cd "${TMP_PREFIX}$1"
     zip "../$1" -r *
     cd ..

pre-commit

@@ -30,7 +30,7 @@ unpack_xlsx () {
 # create a placeholder text file for the .xlsx file, which uniquely identifies
 # it and prevents losing work on a checkout
 replace_with_placeholder () {
-    sha1sum "$1" > "$1"
+    sha1sum "$1" | tee "$1" > /dev/null # hack for overwriting without temp file
 }
 
 
@@ -56,11 +56,14 @@ for i in $(git diff --name-only --cached -- *.xlsx); do
     cd "$dir"
     unpack_xlsx "$file"
     replace_with_placeholder "$file"
+    echo -n "Commit placeholder file: "
+    file "$file"
     reformat_xmls "${TMP_PREFIX}$file"
     cd -
 
-    # stage the XML files
+    # stage the XML files and the placeholder
     git add "$dir/${TMP_PREFIX}$file"
+    git add "$dir/$file"
 done
 
 echo "=== End of pre-commit processing ==="