fix(git): refuse duplicate values, show list errors, Escape on Add

Review findings. With a key holding the same value twice, --fixed-value
--replace-all rewrote both and merged two rows into one, and --unset
failed on both; gitcfg now counts the matches and refuses anything but
exactly one, pointing at the editor. A file git cannot parse made list
print nothing, which the page drew as an empty config; list now prints
git's error as an error= line and the page shows it. Escape in the Add
fields clears the typed text before it leaves the page, as a row's edit
is undone first.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/desktop/modules/git/README.md b/desktop/modules/git/README.md
index 57c8965..e5a4370 100644
--- a/desktop/modules/git/README.md
+++ b/desktop/modules/git/README.md
@@ -13,7 +13,13 @@ its comments and layout. `--fixed-value` makes a write touch one value of a
 multi-valued key. `set` and `unset` first check the old value is still
 there, because `--replace-all` with no match appends instead of failing, and
 the file may have changed in the editor. After every write the page reads
-the list again; a failure shows git's reason under its row.
+the list again; a failure shows git's reason under its row. A value held
+twice by the same key is refused, since git would merge both rows into one
+on edit and cannot remove just one; fix those in the editor. A file git
+cannot parse shows git's error instead of an empty list.
+
+Every reload rebuilds the rows, so an edit typed into one row and not
+saved with Enter is lost when another row is saved or removed.
 
 Checks: `./test-gitcfg.sh` (a throwaway `GIT_CONFIG_GLOBAL`) and
 `node desktop/modules/git/test_git.js`.