Merge branch 'ls/doc-raw-timestamp-prefix' into jch

Documentation and tests have been added to clarify that Git's internal
raw timestamp format requires a `@` prefix for values less than
100,000,000 to prevent ambiguity with other formats like YYYYMMDD.

* ls/doc-raw-timestamp-prefix:
  doc: document and test `@` prefix for raw timestamps
This commit is contained in:
Junio C Hamano
2026-06-04 08:14:00 +09:00
2 changed files with 16 additions and 0 deletions

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@@ -9,6 +9,11 @@ Git internal format::
`<unix-timestamp>` is the number of seconds since the UNIX epoch.
`<time-zone-offset>` is a positive or negative offset from UTC.
For example CET (which is 1 hour ahead of UTC) is `+0100`.
+
It is safer to prepend the `<unix-timestamp>` with `@` (e.g.,
`@0 +0000`), which forces Git to interpret it as a raw timestamp. This
is required for values less than 100,000,000 (which have fewer than 9
digits) to avoid confusion with other date formats like `YYYYMMDD`.
RFC 2822::
The standard date format as described by RFC 2822, for example

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@@ -138,6 +138,13 @@ check_parse '1969-12-31 23:59:59 Z' bad
check_parse '1969-12-31 23:59:59 +11' bad
check_parse '1969-12-31 23:59:59 -11' bad
# pathologically small timestamps requiring `@` prefix
check_parse '@0 +0000' '1970-01-01 00:00:00 +0000'
check_parse '@99999999 +0000' '1973-03-03 09:46:39 +0000'
check_parse '99999999 +0000' bad
check_parse '@100000000 +0000' '1973-03-03 09:46:40 +0000'
check_parse '100000000 +0000' '1973-03-03 09:46:40 +0000'
REQUIRE_64BIT_TIME=HAVE_64BIT_TIME
check_parse '2099-12-31 23:59:59' '2099-12-31 23:59:59 +0000'
check_parse '2099-12-31 23:59:59 +00' '2099-12-31 23:59:59 +0000'
@@ -237,6 +244,10 @@ check_approxidate '6AM, June 7, 2009' '2009-06-07 06:00:00'
check_approxidate '2008-12-01' '2008-12-01 19:20:00'
check_approxidate '2009-12-01' '2009-12-01 19:20:00'
# ambiguous raw timestamp
check_approxidate '2000 +0000' '2000-08-30 19:20:00'
check_approxidate '@2000 +0000' '1970-01-01 00:33:20'
check_date_format_human() {
t=$(($GIT_TEST_DATE_NOW - $1))
echo "$t -> $2" >expect