[PATCH v5 0/5] Fix and extend encoding handling in fast export/import

While stress testing `git filter-repo`, I noticed an issue with encoding; further digging led to the fixes and features in this series. See the individual commit messages for details.

Changes since v4 (full range-diff below):
  * Used git_parse_maybe_bool()
  * Updated Documentation/git-fast-export.txt to document the new option

Elijah Newren (5):
  t9350: fix encoding test to actually test reencoding
  fast-import: support 'encoding' commit header
  fast-export: avoid stripping encoding header if we cannot reencode
  fast-export: differentiate between explicitly utf-8 and implicitly
    utf-8
  fast-export: do automatic reencoding of commit messages only if
    requested

 Documentation/git-fast-export.txt            |  7 ++
 Documentation/git-fast-import.txt            |  7 ++
 builtin/fast-export.c                        | 55 ++++++++++++--
 fast-import.c                                | 11 ++-
 t/t9300-fast-import.sh                       | 20 +++++
 t/t9350-fast-export.sh                       | 78 +++++++++++++++++---
 t/t9350/broken-iso-8859-7-commit-message.txt |  1 +
 t/t9350/simple-iso-8859-7-commit-message.txt |  1 +
 8 files changed, 163 insertions(+), 17 deletions(-)
 create mode 100644 t/t9350/broken-iso-8859-7-commit-message.txt
 create mode 100644 t/t9350/simple-iso-8859-7-commit-message.txt

Range-diff:
1:  37a68a0ffd = 1:  37a68a0ffd t9350: fix encoding test to actually test reencoding
2:  3d84f4613d = 2:  3d84f4613d fast-import: support 'encoding' commit header
3:  baa8394a3a = 3:  baa8394a3a fast-export: avoid stripping encoding header if we cannot reencode
4:  49960164c6 = 4:  49960164c6 fast-export: differentiate between explicitly utf-8 and implicitly utf-8
5:  571613a09e ! 5:  d8be4ee826 fast-export: do automatic reencoding of commit messages only if requested
    @@ -13,6 +13,24 @@
     
         Signed-off-by: Elijah Newren <newren@gmail.com>
     
    + diff --git a/Documentation/git-fast-export.txt b/Documentation/git-fast-export.txt
    + --- a/Documentation/git-fast-export.txt
    + +++ b/Documentation/git-fast-export.txt
    +@@
    + 	for intermediary filters (e.g. for rewriting commit messages
    + 	which refer to older commits, or for stripping blobs by id).
    + 
    ++--reencode=(yes|no|abort)::
    ++	Specify how to handle `encoding` header in commit objects.  When
    ++	asking to 'abort' (which is the default), this program will die
    ++	when encountering such a commit object.  With 'yes', the commit
    ++	message will be reencoded into UTF-8.  With 'no', the original
    ++	encoding will be preserved.
    ++
    + --refspec::
    + 	Apply the specified refspec to each ref exported. Multiple of them can
    + 	be specified.
    +
      diff --git a/builtin/fast-export.c b/builtin/fast-export.c
      --- a/builtin/fast-export.c
      +++ b/builtin/fast-export.c
    @@ -31,14 +49,25 @@
     +static int parse_opt_reencode_mode(const struct option *opt,
     +				   const char *arg, int unset)
     +{
    -+	if (unset || !strcmp(arg, "abort"))
    ++	if (unset) {
     +		reencode_mode = REENCODE_ABORT;
    -+	else if (!strcmp(arg, "yes") || !strcmp(arg, "true") || !strcmp(arg, "on"))
    -+		reencode_mode = REENCODE_YES;
    -+	else if (!strcmp(arg, "no") || !strcmp(arg, "false") || !strcmp(arg, "off"))
    ++		return 0;
    ++	}
    ++
    ++	switch (git_parse_maybe_bool(arg)) {
    ++	case 0:
     +		reencode_mode = REENCODE_NO;
    -+	else
    -+		return error("Unknown reencoding mode: %s", arg);
    ++		break;
    ++	case 1:
    ++		reencode_mode = REENCODE_YES;
    ++		break;
    ++	default:
    ++		if (arg && !strcasecmp(arg, "abort"))
    ++			reencode_mode = REENCODE_ABORT;
    ++		else
    ++			return error("Unknown reencoding mode: %s", arg);
    ++	}
    ++
     +	return 0;
     +}
     +