Implement more gzip compatibility (#3037)

-n --no-name is the current behavior already, so we can implement
this as a noop.

--best is an alias for -9 in gzip

add basic cli tests.

programs/zstd.1

@@ -217,6 +217,17 @@ If input directory contains "\.\.", the files in this directory will be ignored\
 .
 .IP "" 0
 .
+.SS "gzip Operation modifiers"
+When invoked via a \fBgzip\fR symlink, \fBzstd\fR will support further options that intend to mimic the \fBgzip\fR behavior:
+.
+.TP
+\fB\-n\fR, \fB\-\-no\-name\fR
+do not store the original filename and timestamps when compressing a file\. This is the default behavior and hence a no\-op\.
+.
+.TP
+\fB\-\-best\fR
+alias to the option \fB\-9\fR\.
+.
 .SS "Restricted usage of Environment Variables"
 Using environment variables to set parameters has security implications\. Therefore, this avenue is intentionally restricted\. Only \fBZSTD_CLEVEL\fR and \fBZSTD_NBTHREADS\fR are currently supported\. They set the compression level and number of threads to use during compression, respectively\.
 .

programs/zstd.1.md

@@ -280,6 +280,18 @@ the last one takes effect.
 * `--`:
     All arguments after `--` are treated as files
 
+
+### gzip Operation modifiers
+When invoked via a `gzip` symlink, `zstd` will support further
+options that intend to mimic the `gzip` behavior:
+
+* `-n`, `--no-name`:
+    do not store the original filename and timestamps when compressing
+    a file. This is the default behavior and hence a no-op.
+* `--best`:
+    alias to the option `-9`.
+
+
 ### Restricted usage of Environment Variables
 
 Using environment variables to set parameters has security implications.

programs/zstdcli.c

@@ -125,6 +125,15 @@ static void checkLibVersion(void)
 }
 
 
+/*! exeNameMatch() :
+    @return : a non-zero value if exeName matches test, excluding the extension
+   */
+static int exeNameMatch(const char* exeName, const char* test)
+{
+    return !strncmp(exeName, test, strlen(test)) &&
+        (exeName[strlen(test)] == '\0' || exeName[strlen(test)] == '.');
+}
+
 /*-************************************
 *  Command Line
 **************************************/
@@ -153,6 +162,11 @@ static void usage(FILE* f, const char* programName)
     DISPLAY_F(f, "          block devices, etc.\n");
     DISPLAY_F(f, "--rm    : remove source file(s) after successful de/compression \n");
     DISPLAY_F(f, " -k     : preserve source file(s) (default) \n");
+#ifdef ZSTD_GZCOMPRESS
+    if (exeNameMatch(programName, ZSTD_GZ)) {     /* behave like gzip */
+        DISPLAY_F(f, " -n     : do not store original filename when compressing \n");
+    }
+#endif
     DISPLAY_F(f, " -h/-H  : display help/long help and exit \n");
 }
 
@@ -208,6 +222,12 @@ static void usage_advanced(const char* programName)
     DISPLAYOUT( "--ultra : enable levels beyond %i, up to %i (requires more memory) \n", ZSTDCLI_CLEVEL_MAX, ZSTD_maxCLevel());
     DISPLAYOUT( "--long[=#]: enable long distance matching with given window log (default: %u) \n", g_defaultMaxWindowLog);
     DISPLAYOUT( "--fast[=#]: switch to very fast compression levels (default: %u) \n", 1);
+#ifdef ZSTD_GZCOMPRESS
+    if (exeNameMatch(programName, ZSTD_GZ)) {     /* behave like gzip */
+        DISPLAYOUT( "--best  : compatibility alias for -9 \n");
+        DISPLAYOUT( "--no-name : do not store original filename when compressing \n");
+    }
+#endif
     DISPLAYOUT( "--adapt : dynamically adapt compression level to I/O conditions \n");
     DISPLAYOUT( "--[no-]row-match-finder : force enable/disable usage of fast row-based matchfinder for greedy, lazy, and lazy2 strategies \n");
     DISPLAYOUT( "--patch-from=FILE : specify the file to be used as a reference point for zstd's diff engine. \n");
@@ -298,15 +318,6 @@ static const char* lastNameFromPath(const char* path)
     return name;
 }
 
-/*! exeNameMatch() :
-    @return : a non-zero value if exeName matches test, excluding the extension
-   */
-static int exeNameMatch(const char* exeName, const char* test)
-{
-    return !strncmp(exeName, test, strlen(test)) &&
-        (exeName[strlen(test)] == '\0' || exeName[strlen(test)] == '.');
-}
-
 static void errorOut(const char* msg)
 {
     DISPLAY("%s \n", msg); exit(1);
@@ -866,7 +877,10 @@ int main(int argCount, const char* argv[])
     if (exeNameMatch(programName, ZSTD_UNZSTD)) operation=zom_decompress;
     if (exeNameMatch(programName, ZSTD_CAT)) { operation=zom_decompress; FIO_overwriteMode(prefs); forceStdout=1; followLinks=1; outFileName=stdoutmark; g_displayLevel=1; }     /* supports multiple formats */
     if (exeNameMatch(programName, ZSTD_ZCAT)) { operation=zom_decompress; FIO_overwriteMode(prefs); forceStdout=1; followLinks=1; outFileName=stdoutmark; g_displayLevel=1; }    /* behave like zcat, also supports multiple formats */
-    if (exeNameMatch(programName, ZSTD_GZ)) { suffix = GZ_EXTENSION; FIO_setCompressionType(prefs, FIO_gzipCompression); FIO_setRemoveSrcFile(prefs, 1); }        /* behave like gzip */
+    if (exeNameMatch(programName, ZSTD_GZ)) {   /* behave like gzip */
+        suffix = GZ_EXTENSION; FIO_setCompressionType(prefs, FIO_gzipCompression); FIO_setRemoveSrcFile(prefs, 1);
+        dictCLevel = cLevel = 6;  /* gzip default is -6 */
+    }
     if (exeNameMatch(programName, ZSTD_GUNZIP)) { operation=zom_decompress; FIO_setRemoveSrcFile(prefs, 1); }                                                     /* behave like gunzip, also supports multiple formats */
     if (exeNameMatch(programName, ZSTD_GZCAT)) { operation=zom_decompress; FIO_overwriteMode(prefs); forceStdout=1; followLinks=1; outFileName=stdoutmark; g_displayLevel=1; }   /* behave like gzcat, also supports multiple formats */
     if (exeNameMatch(programName, ZSTD_LZMA)) { suffix = LZMA_EXTENSION; FIO_setCompressionType(prefs, FIO_lzmaCompression); FIO_setRemoveSrcFile(prefs, 1); }    /* behave like lzma */
@@ -936,6 +950,10 @@ int main(int argCount, const char* argv[])
                 if (!strcmp(argument, "--format=zstd")) { suffix = ZSTD_EXTENSION; FIO_setCompressionType(prefs, FIO_zstdCompression); continue; }
 #ifdef ZSTD_GZCOMPRESS
                 if (!strcmp(argument, "--format=gzip")) { suffix = GZ_EXTENSION; FIO_setCompressionType(prefs, FIO_gzipCompression); continue; }
+                if (exeNameMatch(programName, ZSTD_GZ)) {     /* behave like gzip */
+                    if (!strcmp(argument, "--best")) { dictCLevel = cLevel = 9; continue; }
+                    if (!strcmp(argument, "--no-name")) { /* ignore for now */; continue; }
+                }
 #endif
 #ifdef ZSTD_LZMACOMPRESS
                 if (!strcmp(argument, "--format=lzma")) { suffix = LZMA_EXTENSION; FIO_setCompressionType(prefs, FIO_lzmaCompression);  continue; }
@@ -1098,6 +1116,9 @@ int main(int argCount, const char* argv[])
                     /* Force stdout, even if stdout==console */
                 case 'c': forceStdout=1; outFileName=stdoutmark; argument++; break;
 
+                    /* do not store filename - gzip compatibility - nothing to do */
+                case 'n': argument++; break;
+
                     /* Use file content as dictionary */
                 case 'D': argument++; NEXT_FIELD(dictFileName); break;