Merge branch 'ar/unconfuse-three-dots'

Ancient part of codebase still shows dots after an abbreviated
object name just to show that it is not a full object name, but
these ellipses are confusing to people who newly discovered Git
who are used to seeing abbreviated object names and find them
confusing with the range syntax.

* ar/unconfuse-three-dots:
  t2020: test variations that matter
  t4013: test new output from diff --abbrev --raw
  diff: diff_aligned_abbrev: remove ellipsis after abbreviated SHA-1 value
  t4013: prepare for upcoming "diff --raw --abbrev" output format change
  checkout: describe_detached_head: remove ellipsis after committish
  print_sha1_ellipsis: introduce helper
  Documentation: user-manual: limit usage of ellipsis
  Documentation: revisions: fix typo: "three dot" ---> "three-dot" (in line with "two-dot").

diff --cc Documentation/git.txt
index e75db10,6ec871b..3f4161a
--- 1/Documentation/git.txt
--- 2/Documentation/git.txt
+++ b/Documentation/git.txt
@@@ -718,24 -709,15 +718,33 @@@ of clones and fetches
        the background which do not want to cause lock contention with
        other operations on the repository.  Defaults to `1`.
  
 +`GIT_REDIRECT_STDIN`::
 +`GIT_REDIRECT_STDOUT`::
 +`GIT_REDIRECT_STDERR`::
 +      Windows-only: allow redirecting the standard input/output/error
 +      handles to paths specified by the environment variables. This is
 +      particularly useful in multi-threaded applications where the
 +      canonical way to pass standard handles via `CreateProcess()` is
 +      not an option because it would require the handles to be marked
 +      inheritable (and consequently *every* spawned process would
 +      inherit them, possibly blocking regular Git operations). The
 +      primary intended use case is to use named pipes for communication
 +      (e.g. `\\.\pipe\my-git-stdin-123`).
 ++
 +Two special values are supported: `off` will simply close the
 +corresponding standard handle, and if `GIT_REDIRECT_STDERR` is
 +`2>&1`, standard error will be redirected to the same handle as
 +standard output.
 +
+ `GIT_PRINT_SHA1_ELLIPSIS` (deprecated)::
+       If set to `yes`, print an ellipsis following an
+       (abbreviated) SHA-1 value.  This affects indications of
+       detached HEADs (linkgit:git-checkout[1]) and the raw
+       diff output (linkgit:git-diff[1]).  Printing an
+       ellipsis in the cases mentioned is no longer considered
+       adequate and support for it is likely to be removed in the
+       foreseeable future (along with the variable).
+ 
  Discussion[[Discussion]]
  ------------------------
  

diff --cc builtin/checkout.c
Simple merge

diff --cc cache.h
Simple merge

diff --cc diff.c
Simple merge

diff --cc environment.c
Simple merge