[PATCH] contrib/completion: avoid empty arithemetic expressions

[David Aguilar <davvid@gmail.com>]

$__git_cmd_idx can be empty in some situations, which leads to
errors when using "git add <tab>", "git mv <tab>",
"git tag <tab>" and "git branch <tab>".

"git mv <tab>" prints this error:

	__git_count_arguments:5:
	bad math expression: operand expected at `""'

	_git_mv:[:9: unknown condition: -gt

"git branch <tab>" prints this error:

	_git_branch:[:4: unknown condition: -lt

"git tag <tab>" prints this error:

	_git_tag:[:3: unknown condition: -lt

"git add <tab>" prints this error:

	__git_find_on_cmdline:[:13: unknown condition: -lt

Fix _git_branch, __git_find_on_cmdline and _git_tag by
initializing the local "c" variable to 1 when empty.

Fix __git_count_arguments by initializing "__git_cmd_idx" to 1.

Adjust the for loop in __git_count_arguments to avoid quoting
the numeric argument to avoid the following error:

	__git_count_arguments:8:
	bad math expression: operand expected at `"1"'

This was tested on zsh 5.7.1 (x86_64-apple-darwin19.0).

Signed-off-by: David Aguilar <davvid@gmail.com>
---
 contrib/completion/git-completion.bash | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 3c5739b905..d51ff5302d 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -1177,6 +1177,9 @@ __git_aliased_command ()
 __git_find_on_cmdline ()
 {
 	local word c="$__git_cmd_idx" show_idx
+	if [ -z "$c" ]; then
+		c=1
+	fi
 
 	while test $# -gt 1; do
 		case "$1" in
@@ -1304,9 +1307,12 @@ __git_has_doubledash ()
 __git_count_arguments ()
 {
 	local word i c=0
+	if [ -z "$__git_cmd_idx" ]; then
+		__git_cmd_idx=1
+	fi
 
 	# Skip "git" (first argument)
-	for ((i="$__git_cmd_idx"; i < ${#words[@]}; i++)); do
+	for ((i=$__git_cmd_idx; i < ${#words[@]}; i++)); do
 		word="${words[i]}"
 
 		case "$word" in
@@ -1448,6 +1454,9 @@ __git_ref_fieldlist="refname objecttype objectsize objectname upstream push HEAD
 _git_branch ()
 {
 	local i c="$__git_cmd_idx" only_local_ref="n" has_r="n"
+	if [ -z "$c" ]; then
+		c=1
+	fi
 
 	while [ $c -lt $cword ]; do
 		i="${words[c]}"
@@ -3213,6 +3222,10 @@ _git_svn ()
 _git_tag ()
 {
 	local i c="$__git_cmd_idx" f=0
+	if [ -z "$c" ]; then
+		c=1
+	fi
+
 	while [ $c -lt $cword ]; do
 		i="${words[c]}"
 		case "$i" in
-- 
2.32.0.rc2.1.g6e92745b1d