learn the "reference" pretty format

On this mailing list (and many others) the standard way to reference other commits with the "reference" format, e.g. "f86a374 (pack-bitmap.c:
fix a memleak, 2015-03-30)". Since it's so commonly used, let's standardise it as a pretty format.

Patches 5-7 were cleanup patches that were critical in earlier iterations of the series but no longer are critical for the rest of the patchset. Nonetheless, let's include them since they improve the quality of the codebase.

Changes since v4:

* Add a column in struct cmt_fmt_map to handle the default short date of --pretty=reference

Changes since v3:

* Change one reference from "summary" to "reference"

* Clarify --pretty=reference documentation

* Add a squashable patch at the end to implement overridable --date

Changes since v2:

* Rename from "summary" to "reference"

* Implement the feature as a canned userformat

* Implement the %*s (short date) format string element

* Remove the enclosing dqs around the subject

Changes since v1:

* Replace more references to "sha1" with "hash"

* Clean up 8/10 by losing the allocation and making the subject less misleading

* Add tests in 7/10 to ensure 8/10 does not change any behaviour

Denton Liu (10):
SubmittingPatches: use generic terms for hash pretty-formats.txt: use generic terms for hash
SubmittingPatches: remove dq from commit reference
completion: complete tformat: pretty format
revision: make get_revision_mark() return const pointer pretty.c: inline initalize format_context
t4205: cover git log --reflog -z blindspot
pretty: add struct cmt_fmt_map::default_date_mode_type
pretty: implement 'reference' format
SubmittingPatches: use --pretty=reference

René Scharfe (1):
pretty: provide short date format

 Documentation/SubmittingPatches        | 16 ++++--
 Documentation/pretty-formats.txt       | 29 +++++++---
 Documentation/pretty-options.txt       |  2 +-
 Documentation/rev-list-options.txt     |  4 +-
 contrib/completion/git-completion.bash |  2 +-
 pretty.c                               | 20 +++++--
 revision.c                             |  4 +-
 revision.h                             |  4 +-
 t/t4205-log-pretty-formats.sh          | 79 ++++++++++++++++++++++++++
 9 files changed, 134 insertions(+), 26 deletions(-)

Range-diff against v4:

 1:  616cda0b4d =  1:  616cda0b4d SubmittingPatches: use generic terms for hash
 2:  badd3d4275 =  2:  badd3d4275 pretty-formats.txt: use generic terms for hash
 3:  ff818446ad =  3:  ff818446ad SubmittingPatches: remove dq from commit reference
 4:  2baa7f8d3d =  4:  2baa7f8d3d completion: complete `tformat:` pretty format
 5:  ac23c4ec45 =  5:  ac23c4ec45 revision: make get_revision_mark() return const pointer
 6:  fa375f8271 =  6:  fa375f8271 pretty.c: inline initalize format_context
 7:  1519677b30 =  7:  1519677b30 t4205: cover `git log --reflog -z` blindspot
 8:  6c41491c3e =  8:  6c41491c3e pretty: provide short date format
 -:  ---------- >  9:  ec05907b62 pretty: add struct cmt_fmt_map::default_date_mode_type
 9:  7b0cf7a39f ! 10:  5264c44fab pretty: implement 'reference' format
    @@ Documentation/pretty-formats.txt: This is designed to be as compact as possible.
     +	  <abbrev hash> (<title line>, <short author date>)
     ++
     +This format is used to refer to another commit in a commit message and
    -+is the same as `--pretty='format:%C(auto)%h (%s, %as)'`.  As with any
    -+`format:` with format placeholders, its output is not affected by other
    -+options like `--decorate` and `--walk-reflogs`.
    ++is the same as `--pretty='format:%C(auto)%h (%s, %ad)'`.  By default,
    ++the date is formatted with `--date=short` unless another `--date` option
    ++is explicitly specified.  As with any `format:` with format
    ++placeholders, its output is not affected by other options like
    ++`--decorate` and `--walk-reflogs`.
     +
      * 'email'
      
    @@ pretty.c: static void setup_commit_formats(void)
     -		{ "oneline",	CMIT_FMT_ONELINE,	1,	0 }
     +		{ "oneline",	CMIT_FMT_ONELINE,	1,	0 },
     +		{ "reference",	CMIT_FMT_USERFORMAT,	1,	0,
    -+			0, "%C(auto)%h (%s, %as)" },
    ++			0, DATE_SHORT, "%C(auto)%h (%s, %ad)" },
      		/*
      		 * Please update $__git_log_pretty_formats in
      		 * git-completion.bash when you add new formats.
    @@ t/t4205-log-pretty-formats.sh: test_expect_success '%S in git log --format works
     +	test_cmp expect actual
     +'
     +
    -+test_expect_success 'log --pretty=reference always uses short date' '
    ++test_expect_success 'log --pretty=reference with log.date is overridden by short date' '
     +	git log --pretty="tformat:%h (%s, %as)" >expect &&
    ++	test_config log.date rfc &&
    ++	git log --pretty=reference >actual &&
    ++	test_cmp expect actual
    ++'
    ++
    ++test_expect_success 'log --pretty=reference with explicit date overrides short date' '
    ++	git log --date=rfc --pretty="tformat:%h (%s, %ad)" >expect &&
     +	git log --date=rfc --pretty=reference >actual &&
     +	test_cmp expect actual
     +'
10:  746481042a = 11:  1281927cb3 SubmittingPatches: use `--pretty=reference`
11:  9d50c069f7 <  -:  ---------- squash! pretty: implement 'reference' format

2.24.0.420.g9ac4901264