From: Lars Schneider <larsxschneider@xxxxxxxxx> UTF supports lossless conversion round tripping and conversions between UTF and other encodings are mostly round trip safe as Unicode aims to be a superset of all other character encodings. However, certain encodings (e.g. SHIFT-JIS) are known to have round trip issues [1]. Add 'core.checkRoundtripEncoding', which contains a comma separated list of encodings, to define for what encodings Git should check the conversion round trip if they are used in the 'working-tree-encoding' attribute. Set SHIFT-JIS as default value for 'core.checkRoundtripEncoding'. [1] https://support.microsoft.com/en-us/help/170559/prb-conversion-problem-between-shift-jis-and-unicode Signed-off-by: Lars Schneider <larsxschneider@xxxxxxxxx> --- Documentation/config.txt | 6 ++++ Documentation/gitattributes.txt | 8 +++++ config.c | 5 +++ convert.c | 78 ++++++++++++++++++++++++++++++++++++++++ convert.h | 1 + environment.c | 1 + t/t0028-working-tree-encoding.sh | 39 ++++++++++++++++++++ 7 files changed, 138 insertions(+) diff --git a/Documentation/config.txt b/Documentation/config.txt index 0e25b2c92b..d7a56054a5 100644 --- a/Documentation/config.txt +++ b/Documentation/config.txt @@ -530,6 +530,12 @@ core.autocrlf:: This variable can be set to 'input', in which case no output conversion is performed. +core.checkRoundtripEncoding:: + A comma separated list of encodings that Git performs UTF-8 round + trip checks on if they are used in an `working-tree-encoding` + attribute (see linkgit:gitattributes[5]). The default value is + `SHIFT-JIS`. + core.symlinks:: If false, symbolic links are checked out as small plain files that contain the link text. linkgit:git-update-index[1] and diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt index 31a4f92840..aa3deae392 100644 --- a/Documentation/gitattributes.txt +++ b/Documentation/gitattributes.txt @@ -312,6 +312,14 @@ number of pitfalls: internal contents as UTF-8 and try to convert it to UTF-16 on checkout. That operation will fail and cause an error. +- Reencoding content to non-UTF encodings can cause errors as the + conversion might not be UTF-8 round trip safe. If you suspect your + encoding to not be round trip safe, then add it to + `core.checkRoundtripEncoding` to make Git check the round trip + encoding (see linkgit:git-config[1]). SHIFT-JIS (Japanese character + set) is known to have round trip issues with UTF-8 and is checked by + default. + - Reencoding content requires resources that might slow down certain Git operations (e.g 'git checkout' or 'git add'). diff --git a/config.c b/config.c index 1f003fbb90..d0ada9fcd4 100644 --- a/config.c +++ b/config.c @@ -1172,6 +1172,11 @@ static int git_default_core_config(const char *var, const char *value) return 0; } + if (!strcmp(var, "core.checkroundtripencoding")) { + check_roundtrip_encoding = xstrdup(value); + return 0; + } + if (!strcmp(var, "core.notesref")) { notes_ref_name = xstrdup(value); return 0; diff --git a/convert.c b/convert.c index eec34a94b9..6cbb2b2618 100644 --- a/convert.c +++ b/convert.c @@ -336,6 +336,43 @@ static void trace_encoding(const char *context, const char *path, strbuf_release(&trace); } +static int check_roundtrip(const char* enc_name) +{ + /* + * check_roundtrip_encoding contains a string of space and/or + * comma separated encodings (eg. "UTF-16, ASCII, CP1125"). + * Search for the given encoding in that string. + */ + const char *found = strcasestr(check_roundtrip_encoding, enc_name); + const char *next; + int len; + if (!found) + return 0; + next = found + strlen(enc_name); + len = strlen(check_roundtrip_encoding); + return (found && ( + /* + * check that the found encoding is at the + * beginning of check_roundtrip_encoding or + * that it is prefixed with a space or comma + */ + found == check_roundtrip_encoding || ( + found > check_roundtrip_encoding && + (*(found-1) == ' ' || *(found-1) == ',') + ) + ) && ( + /* + * check that the found encoding is at the + * end of check_roundtrip_encoding or + * that it is suffixed with a space or comma + */ + next == check_roundtrip_encoding + len || ( + next < check_roundtrip_encoding + len && + (*next == ' ' || *next == ',') + ) + )); +} + static const char *default_encoding = "UTF-8"; static int encode_to_git(const char *path, const char *src, size_t src_len, @@ -384,6 +421,47 @@ static int encode_to_git(const char *path, const char *src, size_t src_len, } trace_encoding("destination", path, default_encoding, dst, dst_len); + /* + * UTF supports lossless conversion round tripping [1] and conversions + * between UTF and other encodings are mostly round trip safe as + * Unicode aims to be a superset of all other character encodings. + * However, certain encodings (e.g. SHIFT-JIS) are known to have round + * trip issues [2]. Check the round trip conversion for all encodings + * listed in core.checkRoundtripEncoding. + * + * The round trip check is only performed if content is written to Git. + * This ensures that no information is lost during conversion to/from + * the internal UTF-8 representation. + * + * Please note, the code below is not tested because I was not able to + * generate a faulty round trip without an iconv error. Iconv errors + * are already caught above. + * + * [1] http://unicode.org/faq/utf_bom.html#gen2 + * [2] https://support.microsoft.com/en-us/help/170559/prb-conversion-problem-between-shift-jis-and-unicode + */ + if (die_on_error && check_roundtrip(enc)) { + char *re_src; + int re_src_len; + + re_src = reencode_string_len(dst, dst_len, + enc, default_encoding, + &re_src_len); + + trace_printf("Checking roundtrip encoding for %s...\n", enc); + trace_encoding("reencoded source", path, enc, + re_src, re_src_len); + + if (!re_src || src_len != re_src_len || + memcmp(src, re_src, src_len)) { + const char* msg = _("encoding '%s' from %s to %s and " + "back is not the same"); + die(msg, path, enc, default_encoding); + } + + free(re_src); + } + strbuf_attach(buf, dst, dst_len, dst_len + 1); return 1; } diff --git a/convert.h b/convert.h index 1d9539ed0b..765abfbd60 100644 --- a/convert.h +++ b/convert.h @@ -56,6 +56,7 @@ struct delayed_checkout { }; extern enum eol core_eol; +extern char *check_roundtrip_encoding; extern const char *get_cached_convert_stats_ascii(const struct index_state *istate, const char *path); extern const char *get_wt_convert_stats_ascii(const char *path); diff --git a/environment.c b/environment.c index 10a32c20ac..5bae9131ad 100644 --- a/environment.c +++ b/environment.c @@ -50,6 +50,7 @@ int check_replace_refs = 1; char *git_replace_ref_base; enum eol core_eol = EOL_UNSET; int global_conv_flags_eol = CONV_EOL_RNDTRP_WARN; +char *check_roundtrip_encoding = "SHIFT-JIS"; unsigned whitespace_rule_cfg = WS_DEFAULT_RULE; enum branch_track git_branch_track = BRANCH_TRACK_REMOTE; enum rebase_setup_type autorebase = AUTOREBASE_NEVER; diff --git a/t/t0028-working-tree-encoding.sh b/t/t0028-working-tree-encoding.sh index bdc487b44f..23e89ae623 100755 --- a/t/t0028-working-tree-encoding.sh +++ b/t/t0028-working-tree-encoding.sh @@ -191,4 +191,43 @@ test_expect_success 'error if encoding garbage is already in Git' ' test_i18ngrep "error: BOM is required" err.out ' +test_expect_success 'check roundtrip encoding' ' + test_when_finished "rm -f roundtrip.shift roundtrip.utf16" && + test_when_finished "git reset --hard HEAD" && + + text="hallo there!\nroundtrip test here!" && + printf "$text" | iconv -f UTF-8 -t SHIFT-JIS >roundtrip.shift && + printf "$text" | iconv -f UTF-8 -t UTF-16 >roundtrip.utf16 && + echo "*.shift text working-tree-encoding=SHIFT-JIS" >>.gitattributes && + + # SHIFT-JIS encoded files are round-trip checked by default... + GIT_TRACE=1 git add .gitattributes roundtrip.shift 2>&1 | + grep "Checking roundtrip encoding for SHIFT-JIS" && + git reset && + + # ... unless we overwrite the Git config! + ! GIT_TRACE=1 git -c core.checkRoundtripEncoding=garbage \ + add .gitattributes roundtrip.shift 2>&1 | + grep "Checking roundtrip encoding for SHIFT-JIS" && + git reset && + + # UTF-16 encoded files should not be round-trip checked by default... + ! GIT_TRACE=1 git add roundtrip.utf16 2>&1 | + grep "Checking roundtrip encoding for UTF-16" && + git reset && + + # ... unless we tell Git to check it! + GIT_TRACE=1 git -c core.checkRoundtripEncoding="UTF-16, UTF-32" \ + add roundtrip.utf16 2>&1 | + grep "Checking roundtrip encoding for UTF-16" && + git reset && + + # ... unless we tell Git to check it! + # (here we also check that the casing of the encoding is irrelevant) + GIT_TRACE=1 git -c core.checkRoundtripEncoding="UTF-32, utf-16" \ + add roundtrip.utf16 2>&1 | + grep "Checking roundtrip encoding for UTF-16" && + git reset +' + test_done -- 2.16.2
