Merge branch 'tk/ambiguous-fetch-refspec'

Give hint when branch tracking cannot be established because fetch
refspecs from multiple remote repositories overlap.

* tk/ambiguous-fetch-refspec:
  tracking branches: add advice to ambiguous refspec error

diff --cc Documentation/config/advice.txt
Simple merge

diff --cc advice.c
Simple merge

diff --cc advice.h
Simple merge

diff --cc branch.c
index 581afd634dad8097aab4d7006661f8395ce40c80,182f1c5a556052d791ae2b0b0e147397e1bb3062..01ecb816d5c4181786e7affab5aabd6a270a1db8
--- 1/branch.c
--- 2/branch.c
+++ b/branch.c
@@@ -232,10 -246,11 +246,14 @@@ static void setup_tracking(const char *
        struct tracking tracking;
        struct string_list tracking_srcs = STRING_LIST_INIT_DUP;
        int config_flags = quiet ? 0 : BRANCH_CONFIG_VERBOSE;
+       struct find_tracked_branch_cb ftb_cb = {
+               .tracking = &tracking,
+               .ambiguous_remotes = STRING_LIST_INIT_DUP,
+       };
  
 +      if (!track)
 +              BUG("asked to set up tracking, but tracking is disallowed");
 +
        memset(&tracking, 0, sizeof(tracking));
        tracking.spec.dst = (char *)orig_ref;
        tracking.srcs = &tracking_srcs;