Avoid unnecessary "if-before-free" tests.

This change removes all obvious useless if-before-free tests.
E.g., it replaces code like this:

        if (some_expression)
                free (some_expression);

with the now-equivalent:

        free (some_expression);

It is equivalent not just because POSIX has required free(NULL)
to work for a long time, but simply because it has worked for
so long that no reasonable porting target fails the test.
Here's some evidence from nearly 1.5 years ago:

    http://www.winehq.org/pipermail/wine-patches/2006-October/031544.html

FYI, the change below was prepared by running the following:

  git ls-files -z | xargs -0 \
  perl -0x3b -pi -e \
    's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*NULL)?\s*\)\s+(free\s*\(\s*\1\s*\))/$2/s'

Note however, that it doesn't handle brace-enclosed blocks like
"if (x) { free (x); }".  But that's ok, since there were none like
that in git sources.

Beware: if you do use the above snippet, note that it can
produce syntactically invalid C code.  That happens when the
affected "if"-statement has a matching "else".
E.g., it would transform this

  if (x)
    free (x);
  else
    foo ();

into this:

  free (x);
  else
    foo ();

There were none of those here, either.

If you're interested in automating detection of the useless
tests, you might like the useless-if-before-free script in gnulib:
[it *does* detect brace-enclosed free statements, and has a --name=S
 option to make it detect free-like functions with different names]

  http://git.sv.gnu.org/gitweb/?p=gnulib.git;a=blob;f=build-aux/useless-if-before-free

Addendum:
  Remove one more (in imap-send.c), spotted by Jean-Luc Herren <jlh@gmx.ch>.

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-blame.c

@@ -123,7 +123,6 @@ static inline struct origin *origin_incref(struct origin *o)
 static void origin_decref(struct origin *o)
 {
 	if (o && --o->refcnt <= 0) {
-		if (o->file.ptr)
 		free(o->file.ptr);
 		free(o);
 	}

builtin-branch.c

@@ -126,7 +126,6 @@ static int delete_branches(int argc, const char **argv, int force, int kinds)
 			continue;
 		}
 
-		if (name)
 		free(name);
 
 		name = xstrdup(mkpath(fmt, argv[i]));
@@ -172,7 +171,6 @@ static int delete_branches(int argc, const char **argv, int force, int kinds)
 		}
 	}
 
-	if (name)
 	free(name);
 
 	return(ret);
@@ -490,7 +488,6 @@ static void create_branch(const char *name, const char *start_name,
 	if (write_ref_sha1(lock, sha1, msg) < 0)
 		die("Failed to write ref: %s.", strerror(errno));
 
-	if (real_ref)
 	free(real_ref);
 }
 

builtin-fast-export.c

@@ -196,7 +196,6 @@ static void handle_commit(struct commit *commit, struct rev_info *rev)
 			  ? strlen(reencoded) : message
 			  ? strlen(message) : 0),
 	       reencoded ? reencoded : message ? message : "");
-	if (reencoded)
 	free(reencoded);
 
 	for (i = 0, p = commit->parents; p; p = p->next) {

builtin-http-fetch.c

@@ -80,7 +80,6 @@ int cmd_http_fetch(int argc, const char **argv, const char *prefix)
 
 	walker_free(walker);
 
-	if (rewritten_url)
 	free(rewritten_url);
 
 	return rc;

builtin-pack-objects.c

@@ -1428,7 +1428,6 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
 	 * accounting lock.  Compiler will optimize the strangeness
 	 * away when THREADED_DELTA_SEARCH is not defined.
 	 */
-	if (trg_entry->delta_data)
 	free(trg_entry->delta_data);
 	cache_lock();
 	if (trg_entry->delta_data) {

builtin-revert.c

@@ -397,7 +397,6 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 		else
 			return execl_git_cmd("commit", "-n", "-F", defmsg, NULL);
 	}
-	if (reencoded_message)
 	free(reencoded_message);
 
 	return 0;

connect.c

@@ -68,7 +68,6 @@ struct ref **get_remote_heads(int in, struct ref **list,
 
 		name_len = strlen(name);
 		if (len != name_len + 41) {
-			if (server_capabilities)
 			free(server_capabilities);
 			server_capabilities = xstrdup(name + name_len + 1);
 		}

diff.c

@@ -118,7 +118,6 @@ static int parse_funcname_pattern(const char *var, const char *ep, const char *v
 		pp->next = funcname_pattern_list;
 		funcname_pattern_list = pp;
 	}
-	if (pp->pattern)
 	free(pp->pattern);
 	pp->pattern = xstrdup(value);
 	return 0;
@@ -492,9 +491,7 @@ static void free_diff_words_data(struct emit_callback *ecbdata)
 				ecbdata->diff_words->plus.text.size)
 			diff_words_show(ecbdata->diff_words);
 
-		if (ecbdata->diff_words->minus.text.ptr)
 		free (ecbdata->diff_words->minus.text.ptr);
-		if (ecbdata->diff_words->plus.text.ptr)
 		free (ecbdata->diff_words->plus.text.ptr);
 		free(ecbdata->diff_words);
 		ecbdata->diff_words = NULL;

dir.c

@@ -704,7 +704,6 @@ static struct path_simplify *create_simplify(const char **pathspec)
 
 static void free_simplify(struct path_simplify *simplify)
 {
-	if (simplify)
 	free(simplify);
 }
 

http-push.c

@@ -664,7 +664,6 @@ static void release_request(struct transfer_request *request)
 		close(request->local_fileno);
 	if (request->local_stream)
 		fclose(request->local_stream);
-	if (request->url != NULL)
 	free(request->url);
 	free(request);
 }
@@ -1283,9 +1282,7 @@ static struct remote_lock *lock_remote(const char *path, long timeout)
 	strbuf_release(&in_buffer);
 
 	if (lock->token == NULL || lock->timeout <= 0) {
-		if (lock->token != NULL)
 		free(lock->token);
-		if (lock->owner != NULL)
 		free(lock->owner);
 		free(url);
 		free(lock);
@@ -1344,7 +1341,6 @@ static int unlock_remote(struct remote_lock *lock)
 			prev->next = prev->next->next;
 	}
 
-	if (lock->owner != NULL)
 	free(lock->owner);
 	free(lock->url);
 	free(lock->token);
@@ -2035,7 +2031,6 @@ static void fetch_symref(const char *path, char **symref, unsigned char *sha1)
 	}
 	free(url);
 
-	if (*symref != NULL)
 	free(*symref);
 	*symref = NULL;
 	hashclr(sha1);
@@ -2435,7 +2430,6 @@ int main(int argc, char **argv)
 	}
 
  cleanup:
-	if (rewritten_url)
 	free(rewritten_url);
 	if (info_ref_lock)
 		unlock_remote(info_ref_lock);

imap-send.c

@@ -472,7 +472,7 @@ v_issue_imap_cmd( imap_store_t *ctx, struct imap_cmd_cb *cb,
 	if (socket_write( &imap->buf.sock, buf, bufl ) != bufl) {
 		free( cmd->cmd );
 		free( cmd );
-		if (cb && cb->data)
+		if (cb)
 			free( cb->data );
 		return NULL;
 	}
@@ -858,7 +858,6 @@ get_cmd_result( imap_store_t *ctx, struct imap_cmd *tcmd )
 		  normal:
 			if (cmdp->cb.done)
 				cmdp->cb.done( ctx, cmdp, resp );
-			if (cmdp->cb.data)
 			free( cmdp->cb.data );
 			free( cmdp->cmd );
 			free( cmdp );

interpolate.c

@@ -11,7 +11,6 @@ void interp_set_entry(struct interp *table, int slot, const char *value)
 	char *oldval = table[slot].value;
 	char *newval = NULL;
 
-	if (oldval)
 	free(oldval);
 
 	if (value)

pretty.c

@@ -30,7 +30,6 @@ enum cmit_fmt get_commit_format(const char *arg)
 	if (*arg == '=')
 		arg++;
 	if (!prefixcmp(arg, "format:")) {
-		if (user_format)
 		free(user_format);
 		user_format = xstrdup(arg + 7);
 		return CMIT_FMT_USERFORMAT;

remote.c

@@ -506,7 +506,6 @@ void free_refs(struct ref *ref)
 	struct ref *next;
 	while (ref) {
 		next = ref->next;
-		if (ref->peer_ref)
 		free(ref->peer_ref);
 		free(ref);
 		ref = next;

setup.c

@@ -448,7 +448,6 @@ int check_repository_format_version(const char *var, const char *value)
 	} else if (strcmp(var, "core.worktree") == 0) {
 		if (!value)
 			return config_error_nonbool(var);
-		if (git_work_tree_cfg)
 		free(git_work_tree_cfg);
 		git_work_tree_cfg = xstrdup(value);
 		inside_work_tree = -1;

sha1_name.c

@@ -625,7 +625,6 @@ static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
 		commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 		if (!parse_object(commit->object.sha1))
 			continue;
-		if (temp_commit_buffer)
 		free(temp_commit_buffer);
 		if (commit->buffer)
 			p = commit->buffer;
@@ -643,7 +642,6 @@ static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
 			break;
 		}
 	}
-	if (temp_commit_buffer)
 	free(temp_commit_buffer);
 	free_commit_list(list);
 	for (l = backup; l; l = l->next)

xdiff-interface.c

@@ -233,7 +233,6 @@ void xdiff_set_find_func(xdemitconf_t *xecfg, const char *value)
 			expression = value;
 		if (regcomp(&reg->re, expression, 0))
 			die("Invalid regexp to look for hunk header: %s", expression);
-		if (buffer)
 		free(buffer);
 		value = ep + 1;
 	}