Add overwrite command

app/Makefile

@@ -184,8 +184,8 @@ endif
 
 ZSV=$(BINDIR)/zsv${EXE}
 
-SOURCES=echo paste count count-pull select select-pull 2tsv 2json serialize flatten pretty stack desc sql 2db compare prop rm mv jq
-CLI_SOURCES=echo select desc count paste 2tsv pretty sql flatten 2json serialize stack 2db compare prop rm mv jq
+SOURCES=echo paste count count-pull select select-pull 2tsv 2json serialize flatten pretty stack desc sql 2db compare prop rm mv jq overwrite
+CLI_SOURCES=echo select desc count paste 2tsv pretty sql flatten 2json serialize stack 2db compare prop rm mv jq overwrite
 
 ifeq ($(ZSVSHEET_BUILD),1)
   SOURCES+=sheet
@@ -290,7 +290,7 @@ help:
 	@echo "which will build and test all apps, or to build/test a single app:"
 	@echo "  ${MAKE} test-xx"
 	@echo "where xx is any of:"
-	@echo "  echo count count-pull paste select select-pull 2tsv 2json serialize flatten pretty stack desc sql 2db prop rm mv"
+	@echo "  echo count count-pull paste select select-pull 2tsv 2json serialize flatten pretty stack desc sql 2db prop rm mv overwrite"
 	@echo ""
 
 install: ${ZSV}

app/builtin/help.c

@@ -55,6 +55,7 @@ static int main_help(int argc, const char *argv[]) {
     "Commands that parse CSV or other tabular data:",
     "  select   : extract rows/columns by name or position and perform other basic and 'cleanup' operations",
     "  echo     : write tabular input to stdout with optional cell overwrites",
+    "  overwrite: save, modify or apply overwrites",
     "  sql      : run ad-hoc SQL",
     "  count    : print the number of rows",
     "  desc     : describe each column",

app/cli.c

@@ -79,6 +79,7 @@ ZSV_MAIN_DECL(compare);
 ZSV_MAIN_DECL(sheet);
 #endif
 ZSV_MAIN_DECL(echo);
+ZSV_MAIN_DECL(overwrite);
 ZSV_MAIN_NO_OPTIONS_DECL(prop);
 ZSV_MAIN_NO_OPTIONS_DECL(rm);
 ZSV_MAIN_NO_OPTIONS_DECL(mv);
@@ -123,6 +124,7 @@ struct builtin_cmd builtin_cmds[] = {
   CLI_BUILTIN_COMMANDEXT(sheet),
 #endif
   CLI_BUILTIN_COMMAND(echo),
+  CLI_BUILTIN_COMMAND(overwrite),
   CLI_BUILTIN_NO_OPTIONS_COMMAND(prop),
   CLI_BUILTIN_NO_OPTIONS_COMMAND(rm),
   CLI_BUILTIN_NO_OPTIONS_COMMAND(mv),

app/ext_example/test/expected/zsvext-test-3.out

@@ -37,6 +37,7 @@ Options common to all commands except `prop`, `rm` and `jq`:
 Commands that parse CSV or other tabular data:
   select   : extract rows/columns by name or position and perform other basic and 'cleanup' operations
   echo     : write tabular input to stdout with optional cell overwrites
+  overwrite: save, modify or apply overwrites
   sql      : run ad-hoc SQL
   count    : print the number of rows
   desc     : describe each column
@@ -95,6 +96,7 @@ Options common to all commands except `prop`, `rm` and `jq`:
 Commands that parse CSV or other tabular data:
   select   : extract rows/columns by name or position and perform other basic and 'cleanup' operations
   echo     : write tabular input to stdout with optional cell overwrites
+  overwrite: save, modify or apply overwrites
   sql      : run ad-hoc SQL
   count    : print the number of rows
   desc     : describe each column