Merge branch 'cc/untracked'

Update the untracked cache subsystem and change its primary UI from
"git update-index" to "git config".

* cc/untracked:
  t7063: add tests for core.untrackedCache
  test-dump-untracked-cache: don't modify the untracked cache
  config: add core.untrackedCache
  dir: simplify untracked cache "ident" field
  dir: add remove_untracked_cache()
  dir: add {new,add}_untracked_cache()
  update-index: move 'uc' var declaration
  update-index: add untracked cache notifications
  update-index: add --test-untracked-cache
  update-index: use enum for untracked cache options
  dir: free untracked cache when removing it

diff --cc Documentation/config.txt
Simple merge

diff --cc builtin/update-index.c
index 7c5c143de5dc74dda2b17832037268fc4e4b9d60,7a5533491eb19ca48556d1fa20bf7cdaf5b50903..dbc23a46b13bee7ff532232c0e1d821c565fd2fb
--- 1/builtin/update-index.c
--- 2/builtin/update-index.c
+++ b/builtin/update-index.c
@@@ -903,8 -910,8 +912,8 @@@ static int reupdate_callback(struct par
  
  int cmd_update_index(int argc, const char **argv, const char *prefix)
  {
 -      int newfd, entries, has_errors = 0, line_termination = '\n';
 +      int newfd, entries, has_errors = 0, nul_term_line = 0;
-       int untracked_cache = -1;
+       enum uc_mode untracked_cache = UC_UNSPECIFIED;
        int read_from_stdin = 0;
        int prefix_length = prefix ? strlen(prefix) : 0;
        int preferred_index_format = 0;

diff --cc cache.h
Simple merge

diff --cc contrib/completion/git-completion.bash
Simple merge

diff --cc dir.c
Simple merge

diff --cc environment.c
Simple merge

diff --cc read-cache.c
Simple merge